Java String Utility Class

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In this article, we will discuss commonly used Java String Utility methods. We can also show you the sample JUnit test cases for String Utility methods.
StringUtility.java class contains very useful String utility methods so you can use them in your day to day project work. These utility methods perform common, often reused functions and they don't require no have object level state, that is they tend to be global functions.
As we know that Java provides built-in functions to handle String operations but there are a few more things we do on a regular basis and can be reused. In this post, we will discuss commonly used and may be helpful to keep handy as StringUtility class with static methods.
Note that the popular frameworks like Spring, Hibernate, and Apache projects use this kind of common String utility classes or methods as reusable methods.
Below class diagram shows a list of utility static methods discussed in this post.
Don't forget to check out to 27 Useful String Utility Methods

StringUtility.java

package com.javaguides.strings;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;

/**
 * 
 * Useful String Utility Methods.
 * 
 * @author javaguides.net
 *
 */
public class StringUtility {

    /**
     * The empty String {@code ""}.
     * 
     * @since 2.0
     */
    public static final String EMPTY = "";

    /**
     * Represents a failed index search.
     * 
     * @since 2.1
     */
    public static final int INDEX_NOT_FOUND = -1;

    public static boolean hasLength(String str) {
        return (str != null && str.length() > 0);
    }

    public static String[] toStringArray(Collection collection) {
        if (collection == null) {
            return null;
        }
        return (String[]) collection.toArray(new String[collection.size()]);
    }

    /**
     * Returns the input argument, but ensures the first character is
     * capitalized (if possible).
     * 
     * @param in
     *            the string to uppercase the first character.
     * @return the input argument, but with the first character capitalized (if
     *         possible).
     * @since 1.2
     */
    public static String uppercaseFirstChar(String in ) {
        if ( in == null || in .length() == 0) {
            return in;
        }
        int length = in .length();
        StringBuilder sb = new StringBuilder(length);

        sb.append(Character.toUpperCase( in .charAt(0)));
        if (length > 1) {
            String remaining = in .substring(1);
            sb.append(remaining);
        }
        return sb.toString();
    }

    // Empty checks
    // -----------------------------------------------------------------------
    /**
     * <p>
     * Checks if a CharSequence is empty ("") or null.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is empty or null
     * @since 3.0 Changed signature from isEmpty(String) to
     *        isEmpty(CharSequence)
     */
    public static boolean isEmpty(final CharSequence cs) {
        return cs == null || cs.length() == 0;
    }

    /**
     * <p>
     * Checks if a CharSequence is not empty ("") and not null.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is not empty and not null
     * @since 3.0 Changed signature from isNotEmpty(String) to
     *        isNotEmpty(CharSequence)
     */
    public static boolean isNotEmpty(final CharSequence cs) {
        return !isEmpty(cs);
    }

    /**
     * <p>
     * Checks if any of the CharSequences are empty ("") or null.
     * </p>
     * 
     * @param css
     *            the CharSequences to check, may be null or empty
     * @return {@code true} if any of the CharSequences are empty or null
     * @since 3.2
     */
    public static boolean isAnyEmpty(final CharSequence...css) {
        if (css != null && css.length == 0) {
            return false;
        }
        for (final CharSequence cs: css) {
            if (isEmpty(cs)) {
                return true;
            }
        }
        return false;
    }

    /**
     * <p>
     * Checks if none of the CharSequences are empty ("") or null.
     * </p>
     * 
     * @param css
     *            the CharSequences to check, may be null or empty
     * @return {@code true} if none of the CharSequences are empty or null
     * @since 3.2
     */
    public static boolean isNoneEmpty(final CharSequence...css) {
        return !isAnyEmpty(css);
    }

    /**
     * <p>
     * Checks if all of the CharSequences are empty ("") or null.
     * </p>
     * 
     * @param css
     *            the CharSequences to check, may be null or empty
     * @return {@code true} if all of the CharSequences are empty or null
     * @since 3.6
     */
    public static boolean isAllEmpty(final CharSequence...css) {
        if (css != null && css.length == 0) {
            return true;
        }
        for (final CharSequence cs: css) {
            if (isNotEmpty(cs)) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if a CharSequence is empty (""), null or whitespace only.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is null, empty or whitespace
     *         only
     * @since 2.0
     * @since 3.0 Changed signature from isBlank(String) to
     *        isBlank(CharSequence)
     */
    public static boolean isBlank(final CharSequence cs) {
        int strLen;
        if (cs == null || (strLen = cs.length()) == 0) {
            return true;
        }
        for (int i = 0; i < strLen; i++) {
            if (!Character.isWhitespace(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if a CharSequence is not empty (""), not null and not whitespace
     * only.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     *
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is not empty and not null and
     *         not whitespace only
     * @since 2.0
     * @since 3.0 Changed signature from isNotBlank(String) to
     *        isNotBlank(CharSequence)
     */
    public static boolean isNotBlank(final CharSequence cs) {
        return !isBlank(cs);
    }

    /**
     * <p>
     * Checks if any of the CharSequences are empty ("") or null or whitespace
     * only.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     * 
     * @param css
     *            the CharSequences to check, may be null or empty
     * @return {@code true} if any of the CharSequences are empty or null or
     *         whitespace only
     * @since 3.2
     */
    public static boolean isAnyBlank(final CharSequence...css) {
        if (css != null && css.length == 0) {
            return false;
        }
        for (final CharSequence cs: css) {
            if (isBlank(cs)) {
                return true;
            }
        }
        return false;
    }

    /**
     * <p>
     * Checks if none of the CharSequences are empty (""), null or whitespace
     * only.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     * 
     * @param css
     *            the CharSequences to check, may be null or empty
     * @return {@code true} if none of the CharSequences are empty or null or
     *         whitespace only
     * @since 3.2
     */
    public static boolean isNoneBlank(final CharSequence...css) {
        return !isAnyBlank(css);
    }

    /**
     * <p>
     * Checks if all of the CharSequences are empty (""), null or whitespace
     * only.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     * 
     * @param css
     *            the CharSequences to check, may be null or empty
     * @return {@code true} if all of the CharSequences are empty or null or
     *         whitespace only
     * @since 3.6
     */
    public static boolean isAllBlank(final CharSequence...css) {
        if (css != null && css.length == 0) {
            return true;
        }
        for (final CharSequence cs: css) {
            if (isNotBlank(cs)) {
                return false;
            }
        }
        return true;
    }

    // Compare
    // -----------------------------------------------------------------------

    public static int compare(final String str1, final String str2) {
        return compare(str1, str2, true);
    }

    public static int compare(final String str1, final String str2, final boolean nullIsLess) {
        if (str1 == str2) {
            return 0;
        }
        if (str1 == null) {
            return nullIsLess ? -1 : 1;
        }
        if (str2 == null) {
            return nullIsLess ? 1 : -1;
        }
        return str1.compareTo(str2);
    }

    public static int compareIgnoreCase(final String str1, final String str2) {
        return compareIgnoreCase(str1, str2, true);
    }

    public static int compareIgnoreCase(final String str1, final String str2, final boolean nullIsLess) {
        if (str1 == str2) {
            return 0;
        }
        if (str1 == null) {
            return nullIsLess ? -1 : 1;
        }
        if (str2 == null) {
            return nullIsLess ? 1 : -1;
        }
        return str1.compareToIgnoreCase(str2);
    }

    /**
     * <p>
     * Check whether the given CharSequence contains any whitespace characters.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     *
     * @param seq
     *            the CharSequence to check (may be {@code null})
     * @return {@code true} if the CharSequence is not empty and contains at
     *         least 1 (breaking) whitespace character
     * @since 3.0
     */
    public static boolean containsWhitespace(final CharSequence seq) {
        if (isEmpty(seq)) {
            return false;
        }
        final int strLen = seq.length();
        for (int i = 0; i < strLen; i++) {
            if (Character.isWhitespace(seq.charAt(i))) {
                return true;
            }
        }
        return false;
    }

    // Case conversion
    // -----------------------------------------------------------------------
    /**
     * <p>
     * Converts a String to upper case as per {@link String#toUpperCase()}.
     * </p>
     *
     * <p>
     * A {@code null} input String returns {@code null}.
     * </p>
     *
     * @param str
     *            the String to upper case, may be null
     * @return the upper cased String, {@code null} if null String input
     */
    public static String upperCase(final String str) {
        if (str == null) {
            return null;
        }
        return str.toUpperCase();
    }

    /**
     * <p>
     * Converts a String to upper case as per
     * {@link String#toUpperCase(Locale)}.
     * </p>
     *
     * <p>
     * A {@code null} input String returns {@code null}.
     * </p>
     *
     * @param str
     *            the String to upper case, may be null
     * @param locale
     *            the locale that defines the case transformation rules, must
     *            not be null
     * @return the upper cased String, {@code null} if null String input
     * @since 2.5
     */
    public static String upperCase(final String str, final Locale locale) {
        if (str == null) {
            return null;
        }
        return str.toUpperCase(locale);
    }

    /**
     * <p>
     * Converts a String to lower case as per {@link String#toLowerCase()}.
     * </p>
     *
     * <p>
     * A {@code null} input String returns {@code null}.
     * </p>
     *
     * @param str
     *            the String to lower case, may be null
     * @return the lower cased String, {@code null} if null String input
     */
    public static String lowerCase(final String str) {
        if (str == null) {
            return null;
        }
        return str.toLowerCase();
    }

    /**
     * <p>
     * Converts a String to lower case as per
     * {@link String#toLowerCase(Locale)}.
     * </p>
     *
     * <p>
     * A {@code null} input String returns {@code null}.
     * </p>
     *
     * @param str
     *            the String to lower case, may be null
     * @param locale
     *            the locale that defines the case transformation rules, must
     *            not be null
     * @return the lower cased String, {@code null} if null String input
     * @since 2.5
     */
    public static String lowerCase(final String str, final Locale locale) {
        if (str == null) {
            return null;
        }
        return str.toLowerCase(locale);
    }

    /**
     * <p>
     * Counts how many times the char appears in the given string.
     * </p>
     *
     * <p>
     * A {@code null} or empty ("") String input returns {@code 0}.
     * </p>
     * 
     * @param str
     *            the CharSequence to check, may be null
     * @param ch
     *            the char to count
     * @return the number of occurrences, 0 if the CharSequence is {@code null}
     * @since 3.4
     */
    public static int countMatches(final CharSequence str, final char ch) {
        if (isEmpty(str)) {
            return 0;
        }
        int count = 0;
        // We could also call str.toCharArray() for faster look ups but that
        // would generate more garbage.
        for (int i = 0; i < str.length(); i++) {
            if (ch == str.charAt(i)) {
                count++;
            }
        }
        return count;
    }

    // Character Tests
    // -----------------------------------------------------------------------
    /**
     * <p>
     * Checks if the CharSequence contains only Unicode letters.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * (length()=0) will return {@code false}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains letters, and is non-null
     * @since 3.0 Changed signature from isAlpha(String) to
     *        isAlpha(CharSequence)
     * @since 3.0 Changed "" to return false and not true
     */
    public static boolean isAlpha(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetter(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains only Unicode letters and space (' ').
     * </p>
     *
     * <p>
     * {@code null} will return {@code false} An empty CharSequence (length()=0)
     * will return {@code true}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains letters and space, and is non-null
     * @since 3.0 Changed signature from isAlphaSpace(String) to
     *        isAlphaSpace(CharSequence)
     */
    public static boolean isAlphaSpace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetter(cs.charAt(i)) && cs.charAt(i) != ' ') {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains only Unicode letters or digits.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * (length()=0) will return {@code false}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains letters or digits, and is non-null
     * @since 3.0 Changed signature from isAlphanumeric(String) to
     *        isAlphanumeric(CharSequence)
     * @since 3.0 Changed "" to return false and not true
     */
    public static boolean isAlphanumeric(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetterOrDigit(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains only Unicode letters, digits or space
     * ({@code ' '}).
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * (length()=0) will return {@code true}.
     * </p>
     *
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains letters, digits or space, and is
     *         non-null
     * @since 3.0 Changed signature from isAlphanumericSpace(String) to
     *        isAlphanumericSpace(CharSequence)
     */
    public static boolean isAlphanumericSpace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLetterOrDigit(cs.charAt(i)) && cs.charAt(i) != ' ') {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains only Unicode digits. A decimal point
     * is not a Unicode digit and returns false.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * (length()=0) will return {@code false}.
     * </p>
     *
     * <p>
     * Note that the method does not allow for a leading sign, either positive
     * or negative. Also, if a String passes the numeric test, it may still
     * generate a NumberFormatException when parsed by Integer.parseInt or
     * Long.parseLong, e.g. if the value is outside the range for int or long
     * respectively.
     * </p>
     *
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains digits, and is non-null
     * @since 3.0 Changed signature from isNumeric(String) to
     *        isNumeric(CharSequence)
     * @since 3.0 Changed "" to return false and not true
     */
    public static boolean isNumeric(final CharSequence cs) {
        if (isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isDigit(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains only Unicode digits or space
     * ({@code ' '}). A decimal point is not a Unicode digit and returns false.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * (length()=0) will return {@code true}.
     * </p>
     *
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains digits or space, and is non-null
     * @since 3.0 Changed signature from isNumericSpace(String) to
     *        isNumericSpace(CharSequence)
     */
    public static boolean isNumericSpace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isDigit(cs.charAt(i)) && cs.charAt(i) != ' ') {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if a String {@code str} contains Unicode digits, if yes then
     * concatenate all the digits in {@code str} and return it as a String.
     * </p>
     *
     * <p>
     * An empty ("") String will be returned if no digits found in {@code str}.
     * </p>
     * 
     * @param str
     *            the String to extract digits from, may be null
     * @return String with only digits, or an empty ("") String if no digits
     *         found, or {@code null} String if {@code str} is null
     * @since 3.6
     */
    public static String getDigits(final String str) {
        if (isEmpty(str)) {
            return str;
        }
        final int sz = str.length();
        final StringBuilder strDigits = new StringBuilder(sz);
        for (int i = 0; i < sz; i++) {
            final char tempChar = str.charAt(i);
            if (Character.isDigit(tempChar)) {
                strDigits.append(tempChar);
            }
        }
        return strDigits.toString();
    }

    /**
     * <p>
     * Checks if the CharSequence contains only whitespace.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * (length()=0) will return {@code true}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains whitespace, and is non-null
     * @since 2.0
     * @since 3.0 Changed signature from isWhitespace(String) to
     *        isWhitespace(CharSequence)
     */
    public static boolean isWhitespace(final CharSequence cs) {
        if (cs == null) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isWhitespace(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains only lowercase characters.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * (length()=0) will return {@code false}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains lowercase characters, and is
     *         non-null
     * @since 2.5
     * @since 3.0 Changed signature from isAllLowerCase(String) to
     *        isAllLowerCase(CharSequence)
     */
    public static boolean isAllLowerCase(final CharSequence cs) {
        if (cs == null || isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isLowerCase(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains only uppercase characters.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty String (length()=0) will
     * return {@code false}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if only contains uppercase characters, and is
     *         non-null
     * @since 2.5
     * @since 3.0 Changed signature from isAllUpperCase(String) to
     *        isAllUpperCase(CharSequence)
     */
    public static boolean isAllUpperCase(final CharSequence cs) {
        if (cs == null || isEmpty(cs)) {
            return false;
        }
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (!Character.isUpperCase(cs.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>
     * Checks if the CharSequence contains mixed casing of both uppercase and
     * lowercase characters.
     * </p>
     *
     * <p>
     * {@code null} will return {@code false}. An empty CharSequence
     * ({@code length()=0}) will return {@code false}.
     * </p>
     * 
     * @param cs
     *            the CharSequence to check, may be null
     * @return {@code true} if the CharSequence contains both uppercase and
     *         lowercase characters
     * @since 3.5
     */
    public static boolean isMixedCase(final CharSequence cs) {
        if (isEmpty(cs) || cs.length() == 1) {
            return false;
        }
        boolean containsUppercase = false;
        boolean containsLowercase = false;
        final int sz = cs.length();
        for (int i = 0; i < sz; i++) {
            if (containsUppercase && containsLowercase) {
                return true;
            } else if (Character.isUpperCase(cs.charAt(i))) {
                containsUppercase = true;
            } else if (Character.isLowerCase(cs.charAt(i))) {
                containsLowercase = true;
            }
        }
        return containsUppercase && containsLowercase;
    }

    // Defaults
    // -----------------------------------------------------------------------
    /**
     * <p>
     * Returns either the passed in String, or if the String is {@code null}, an
     * empty String ("").
     * </p>
     * 
     * @see ObjectUtils#toString(Object)
     * @see String#valueOf(Object)
     * @param str
     *            the String to check, may be null
     * @return the passed in String, or the empty String if it was {@code null}
     */
    public static String defaultString(final String str) {
        return defaultString(str, EMPTY);
    }

    /**
     * <p>
     * Returns either the passed in String, or if the String is {@code null},
     * the value of {@code defaultStr}.
     * </p>
     * 
     * @see ObjectUtils#toString(Object,String)
     * @see String#valueOf(Object)
     * @param str
     *            the String to check, may be null
     * @param defaultStr
     *            the default String to return if the input is {@code null}, may
     *            be null
     * @return the passed in String, or the default if it was {@code null}
     */
    public static String defaultString(final String str, final String defaultStr) {
        return str == null ? defaultStr : str;
    }

    /**
     * <p>
     * Returns the first value in the array which is not empty (""),
     * {@code null} or whitespace only.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     *
     * <p>
     * If all values are blank or the array is {@code null} or empty then
     * {@code null} is returned.
     * </p>
     * 
     * @param <T>
     *            the specific kind of CharSequence
     * @param values
     *            the values to test, may be {@code null} or empty
     * @return the first value from {@code values} which is not blank, or
     *         {@code null} if there are no non-blank values
     * @since 3.8
     */
    @SafeVarargs
    public static < T extends CharSequence > T firstNonBlank(final T...values) {
        if (values != null) {
            for (final T val: values) {
                if (isNotBlank(val)) {
                    return val;
                }
            }
        }
        return null;
    }

    /**
     * <p>
     * Returns the first value in the array which is not empty.
     * </p>
     *
     * <p>
     * If all values are empty or the array is {@code null} or empty then
     * {@code null} is returned.
     * </p>
     * 
     * @param <T>
     *            the specific kind of CharSequence
     * @param values
     *            the values to test, may be {@code null} or empty
     * @return the first value from {@code values} which is not empty, or
     *         {@code null} if there are no non-empty values
     * @since 3.8
     */
    @SafeVarargs
    public static < T extends CharSequence > T firstNonEmpty(final T...values) {
        if (values != null) {
            for (final T val: values) {
                if (isNotEmpty(val)) {
                    return val;
                }
            }
        }
        return null;
    }

    /**
     * <p>
     * Returns either the passed in CharSequence, or if the CharSequence is
     * whitespace, empty ("") or {@code null}, the value of {@code defaultStr}.
     * </p>
     *
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}.
     * </p>
     * 
     * @param <T>
     *            the specific kind of CharSequence
     * @param str
     *            the CharSequence to check, may be null
     * @param defaultStr
     *            the default CharSequence to return if the input is whitespace,
     *            empty ("") or {@code null}, may be null
     * @return the passed in CharSequence, or the default
     * @see StringUtils#defaultString(String, String)
     */
    public static < T extends CharSequence > T defaultIfBlank(final T str, final T defaultStr) {
        return isBlank(str) ? defaultStr : str;
    }

    /**
     * <p>
     * Returns either the passed in CharSequence, or if the CharSequence is
     * empty or {@code null}, the value of {@code defaultStr}.
     * </p>
     *
     * @param <T>
     *            the specific kind of CharSequence
     * @param str
     *            the CharSequence to check, may be null
     * @param defaultStr
     *            the default CharSequence to return if the input is empty ("")
     *            or {@code null}, may be null
     * @return the passed in CharSequence, or the default
     * @see StringUtils#defaultString(String, String)
     */
    public static < T extends CharSequence > T defaultIfEmpty(final T str, final T defaultStr) {
        return isEmpty(str) ? defaultStr : str;
    }

    /**
     * Trim leading and trailing whitespace from the given {@code String}.
     * 
     * @param str
     *            the {@code String} to check
     * @return the trimmed {@code String}
     * @see java.lang.Character#isWhitespace
     */
    public static String trimWhitespace(String str) {
        if (!hasLength(str)) {
            return str;
        }

        int beginIndex = 0;
        int endIndex = str.length() - 1;

        while (beginIndex <= endIndex && Character.isWhitespace(str.charAt(beginIndex))) {
            beginIndex++;
        }

        while (endIndex > beginIndex && Character.isWhitespace(str.charAt(endIndex))) {
            endIndex--;
        }

        return str.substring(beginIndex, endIndex + 1);
    }

    /**
     * Trim <i>all</i> whitespace from the given {@code String}: leading,
     * trailing, and in between characters.
     * 
     * @param str
     *            the {@code String} to check
     * @return the trimmed {@code String}
     * @see java.lang.Character#isWhitespace
     */
    public static String trimAllWhitespace(String str) {
        if (!hasLength(str)) {
            return str;
        }

        int len = str.length();
        StringBuilder sb = new StringBuilder(str.length());
        for (int i = 0; i < len; i++) {
            char c = str.charAt(i);
            if (!Character.isWhitespace(c)) {
                sb.append(c);
            }
        }
        return sb.toString();
    }

    /**
     * Trim leading whitespace from the given {@code String}.
     * 
     * @param str
     *            the {@code String} to check
     * @return the trimmed {@code String}
     * @see java.lang.Character#isWhitespace
     */
    public static String trimLeadingWhitespace(String str) {
        if (!hasLength(str)) {
            return str;
        }

        StringBuilder sb = new StringBuilder(str);
        while (sb.length() > 0 && Character.isWhitespace(sb.charAt(0))) {
            sb.deleteCharAt(0);
        }
        return sb.toString();
    }

    /**
     * Trim trailing whitespace from the given {@code String}.
     * 
     * @param str
     *            the {@code String} to check
     * @return the trimmed {@code String}
     * @see java.lang.Character#isWhitespace
     */
    public static String trimTrailingWhitespace(String str) {
        if (!hasLength(str)) {
            return str;
        }

        StringBuilder sb = new StringBuilder(str);
        while (sb.length() > 0 && Character.isWhitespace(sb.charAt(sb.length() - 1))) {
            sb.deleteCharAt(sb.length() - 1);
        }
        return sb.toString();
    }

    /**
     * Trim all occurrences of the supplied leading character from the given
     * {@code String}.
     * 
     * @param str
     *            the {@code String} to check
     * @param leadingCharacter
     *            the leading character to be trimmed
     * @return the trimmed {@code String}
     */
    public static String trimLeadingCharacter(String str, char leadingCharacter) {
        if (!hasLength(str)) {
            return str;
        }

        StringBuilder sb = new StringBuilder(str);
        while (sb.length() > 0 && sb.charAt(0) == leadingCharacter) {
            sb.deleteCharAt(0);
        }
        return sb.toString();
    }

    /**
     * Trim all occurrences of the supplied trailing character from the given
     * {@code String}.
     * 
     * @param str
     *            the {@code String} to check
     * @param trailingCharacter
     *            the trailing character to be trimmed
     * @return the trimmed {@code String}
     */
    public static String trimTrailingCharacter(String str, char trailingCharacter) {
        if (!hasLength(str)) {
            return str;
        }

        StringBuilder sb = new StringBuilder(str);
        while (sb.length() > 0 && sb.charAt(sb.length() - 1) == trailingCharacter) {
            sb.deleteCharAt(sb.length() - 1);
        }
        return sb.toString();
    }

    /**
     * Test if the given {@code String} starts with the specified prefix,
     * ignoring upper/lower case.
     * 
     * @param str
     *            the {@code String} to check
     * @param prefix
     *            the prefix to look for
     * @see java.lang.String#startsWith
     */
    public static boolean startsWithIgnoreCase(String str, String prefix) {
        return (str != null && prefix != null && str.length() >= prefix.length() &&
            str.regionMatches(true, 0, prefix, 0, prefix.length()));
    }

    /**
     * Quote the given {@code String} with single quotes.
     * 
     * @param str
     *            the input {@code String} (e.g. "myString")
     * @return the quoted {@code String} (e.g. "'myString'"), or {@code null} if
     *         the input was {@code null}
     */

    public static String quote(String str) {
        return (str != null ? "'" + str + "'" : null);
    }

    /**
     * Turn the given Object into a {@code String} with single quotes if it is a
     * {@code String}; keeping the Object as-is else.
     * 
     * @param obj
     *            the input Object (e.g. "myString")
     * @return the quoted {@code String} (e.g. "'myString'"), or the input
     *         object as-is if not a {@code String}
     */

    public static Object quoteIfString(Object obj) {
        return (obj instanceof String ? quote((String) obj) : obj);
    }

    /**
     * Converts an {@link InputStream} into a String.
     * 
     * @param inputStream
     *            The input stream to convert
     * @return A String containing the contents of the {@link InputStream}
     */
    public static String fromInputStream(InputStream inputStream) {
        InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
        return fromBufferedReader(bufferedReader);
    }

    /**
     * Converts a {@link BufferedReader} into a String.
     * 
     * @param bufferedReader
     *            The {@link BufferedReader} to convert
     * @return A String containing the contents of the {@link BufferedReader}
     */
    public static String fromBufferedReader(BufferedReader bufferedReader) {
        StringBuffer sb = new StringBuffer();

        try {
            String line = bufferedReader.readLine();

            while (line != null) {
                sb.append(line);
                line = bufferedReader.readLine();
                if (line != null) {
                    sb.append("\n");
                }
            }
        } catch (IOException e) {
            // replace this with log.error
            e.printStackTrace();
        }

        return sb.toString();
    }

    public static String getClasspath() {
        Properties prop = System.getProperties();
        return prop.getProperty("java.class.path", null);
    }

    public static String getAllFilesOnClasspath() {
        StringBuffer sb = new StringBuffer();
        for (final java.lang.String path: getClasspath().split(":")) {
            final java.io.File object = new java.io.File(path);
            if (object.isDirectory()) {
                for (File file: object.listFiles()) {
                    sb.append(file.getAbsolutePath()).append("\n");
                }
            } else if (object.isFile()) {
                sb.append(object).append("\n");
            }
        }
        return sb.toString();
    }

    /**
     * Converts a 2 dimensional array into a map where the first dimension is 2
     * cell String array containing key and value respectively. Any array with
     * fewer than 2 elements is ignored.
     * 
     * @param array
     *            The array to convert into a map
     * @return A {@link Map} of key value pairs extracted from the supplied
     *         array.
     */
    public static Map < String, String > arrayToMap(String[][] array) {
        Map < String, String > map = new HashMap < String, String > ();

        for (String[] pair: array) {
            if (pair.length > 1) {
                // got a pair, add to map
                map.put(pair[0], pair[1]);
            }
        }

        return map;
    }

    /**
     * Searches through a given String array and returns an element that starts
     * with the supplied startsWith string. This method ignores the case. If no
     * match can be found then an empty String is returned.
     * 
     * @param array
     *            The array of Strings to search through
     * @param startsWith
     *            The String to match.
     * @return A String that starts with startsWith (ignoring case) or an empty
     *         String if one cannot be found. If multiple Strings match, then
     *         the first one in the array will be returned.
     */
    public static String startsWith(String[] array, String startsWith) {
        String lcStartsWith = startsWith.toLowerCase();
        for (String element: array) {
            if (element.toLowerCase().startsWith(lcStartsWith)) {
                return element;
            }
        }

        return "";
    }

    /**
     * Iterates over the array looking for an element that, ignoring case starts
     * with the startsWith string. If a match is found then the index of the
     * matching element is returned. If no match is found then -1 is returned.
     * 
     * @param array
     *            The array of String to search through.
     * @param startsWith
     *            The String to match against
     * @return Index of the matching element, or -1 if no match is found. If
     *         there are multiple matches then the index of the first match is
     *         returned.
     */
    public static int indexThatStartsWith(String[] array, String startsWith) {
        String lcStartsWith = startsWith.toLowerCase();

        for (int i = 0; i < array.length; i++) {
            if (array[i].toLowerCase().startsWith(lcStartsWith)) {
                return i;
            }
        }

        return -1;
    }

    /**
     * Keeps prepending a given prependChar to an initialInt until it reaches
     * the targetLength and returns the result. If initialInt is null then null
     * is returned.
     * 
     * @param prependChar
     *            The char to prepend
     * @param targetLength
     *            The targetLength
     * @param initialInt
     *            The initial Integer
     * @return The initialInt padded out with the prependChar at the beginning
     *         of the string until it reaches the targetLength
     */
    public static String prependToLength(char prependChar, int targetLength, Integer initialInt) {

        if (initialInt == null) {
            return null;
        }

        return prependToLength(prependChar, targetLength, initialInt.toString());
    }

    /**
     * Keeps prepending a given prependChar to an initialString until it reaches
     * the targetLength and returns the result. If initialString is null then
     * null is returned.
     * 
     * @param prependChar
     *            The char to prepend
     * @param targetLength
     *            The targetLength
     * @param initialString
     *            The initiatlString
     * @return The initialString padded out with the prependChar at the
     *         beginning of the string until it reaches the targetLength
     */
    public static String prependToLength(char prependChar, int targetLength, String initialString) {
        if (initialString == null) {
            return null;
        }

        StringBuffer result = new StringBuffer(initialString);

        while (result.length() < targetLength) {
            result.append(prependChar);
        }

        return result.reverse().toString();
    }

    /**
     * If a given string is longer than maxLength then it is truncated. For
     * example if str="hamburger" and maxLength=3 then "ham" will be returned.
     * 
     * @param str
     *            The str to be truncated. If this is null or equal to or
     *            shorter than maxLength then it is returned whithout
     *            modification.
     * @param maxLength
     *            Maximum length of the returned String. If this is less than 1,
     *            then str is returned regardless.
     * @return A string no more than maxLength characters in length.
     */
    public static String truncate(String str, int maxLength) {
        if (str == null || str.length() <= maxLength || maxLength < 1) {
            return str;
        }

        return str.substring(0, maxLength);
    }

    /**
     * This String utility or util method can be used to merge 2 arrays of
     * string values. If the input arrays are like this array1 = {"a", "b" ,
     * "c"} array2 = {"c", "d", "e"} Then the output array will have {"a", "b" ,
     * "c", "d", "e"}
     * 
     * This takes care of eliminating duplicates and checks null values.
     * 
     * @param values
     * @return
     */
    public static String[] mergeStringArrays(String array1[], String array2[]) {

        if (array1 == null || array1.length == 0)
            return array2;
        if (array2 == null || array2.length == 0)
            return array1;
        List < String > array1List = Arrays.asList(array1);
        List < String > array2List = Arrays.asList(array2);
        List < String > result = new ArrayList < String > (array1List);
        List < String > tmp = new ArrayList < String > (array1List);
        tmp.retainAll(array2List);
        result.removeAll(tmp);
        result.addAll(array2List);
        return ((String[]) result.toArray(new String[result.size()]));
    }

    public static void main(String[] args) {
        String[] strArray = mergeStringArrays(new String[] {
            "abc",
            "xyz",
            "pqr"
        }, new String[] {
            "ABC",
            "PQR"
        });
        for (String string: strArray) {
            System.out.println(string);
        }
    }
}

StringUtilityTest.java

JUnit test cases for String Utility methods.
package com.javaguides.strings;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;

import org.junit.Test;

/**
 *  JUnit test cases for StringUtility Methods
 * @author javaguides.net
 *
 */

public class StringUtilityTest {

    @Test
    public void hasLengthTest() {
        assertFalse(StringUtility.hasLength(null));
        assertFalse(StringUtility.hasLength(""));
        assertTrue(StringUtility.hasLength(" "));
        assertTrue(StringUtility.hasLength("javaguides"));
    }

    @Test
    public void toStringArrayTest() {
        String[] strArray = StringUtility.toStringArray(Arrays.asList("a", "b", "c"));
        for (int i = 0; i < strArray.length; i++) {
            System.out.println(strArray[i]);
            assertNotNull(strArray[i]);
        }
    }

    @Test
    public void uppercaseFirstCharTest() {
        assertEquals("Javaguides", StringUtility.uppercaseFirstChar("javaguides"));
        assertEquals("Java", StringUtility.uppercaseFirstChar("java"));
        System.out.println(StringUtility.uppercaseFirstChar("javaguides"));
    }

    @Test
    public void isNotBlankTest() {
        assertFalse(StringUtility.isNotBlank(null));
        assertFalse(StringUtility.isNotBlank(""));
        assertFalse(StringUtility.isNotBlank(" "));
        assertTrue(StringUtility.isNotBlank("bob"));
        assertTrue(StringUtility.isNotBlank("  bob  "));
    }

    @Test
    public void isEmptyTest() {
        assertTrue(StringUtility.isEmpty(null));
        assertTrue(StringUtility.isEmpty(""));
        assertFalse(StringUtility.isEmpty(" "));
        assertFalse(StringUtility.isEmpty("bob"));
        assertFalse(StringUtility.isEmpty("  bob  "));
    }

    @Test
    public void isBlankTest() {
        assertTrue(StringUtility.isBlank(null));
        assertTrue(StringUtility.isBlank(""));
        assertTrue(StringUtility.isBlank(" "));
        assertFalse(StringUtility.isBlank("bob"));
        assertFalse(StringUtility.isBlank("  bob  "));
    }

    @Test
    public void isAnyEmptyTest() {
        assertTrue(StringUtility.isAnyEmpty((String) null));
        assertFalse(StringUtility.isAnyEmpty((String[]) null));
        assertTrue(StringUtility.isAnyEmpty(null, "foo"));
        assertTrue(StringUtility.isAnyEmpty("", "bar"));
        assertTrue(StringUtility.isAnyEmpty("bob", ""));
        assertTrue(StringUtility.isAnyEmpty("  bob  ", null));
        assertFalse(StringUtility.isAnyEmpty(" ", "bar"));
        assertFalse(StringUtility.isAnyEmpty("foo", "bar"));
        assertFalse(StringUtility.isAnyEmpty(new String[] {}));
        assertTrue(StringUtility.isAnyEmpty(new String[] {
            ""
        }));
    }

    @Test
    public void isAnyBlankTest() {
        assertFalse(StringUtility.isAnyBlank((String[]) null));
        assertTrue(StringUtility.isAnyBlank((String) null));
        assertTrue(StringUtility.isAnyBlank(null, "foo"));
        assertTrue(StringUtility.isAnyBlank(null, null));
        assertTrue(StringUtility.isAnyBlank("", "bar"));
        assertTrue(StringUtility.isAnyBlank("bob", ""));
        assertTrue(StringUtility.isAnyBlank("  bob  ", null));
        assertTrue(StringUtility.isAnyBlank(" ", "bar"));
        assertFalse(StringUtility.isAnyBlank(new String[] {}));
        assertTrue(StringUtility.isAnyBlank(new String[] {
            ""
        }));
        assertFalse(StringUtility.isAnyBlank("foo", "bar"));
    }

    @Test
    public void testContainsWhitespace() {
        assertFalse(StringUtility.containsWhitespace(null));
        assertFalse(StringUtility.containsWhitespace(""));
        assertFalse(StringUtility.containsWhitespace("a"));
        assertFalse(StringUtility.containsWhitespace("abc"));
        assertTrue(StringUtility.containsWhitespace(" "));
        assertTrue(StringUtility.containsWhitespace(" a"));
        assertTrue(StringUtility.containsWhitespace("abc "));
        assertTrue(StringUtility.containsWhitespace("a b"));
        assertTrue(StringUtility.containsWhitespace("a  b"));
    }

    @Test
    public void testTrimWhitespace() {
        assertEquals(null, StringUtility.trimWhitespace(null));
        assertEquals("", StringUtility.trimWhitespace(""));
        assertEquals("", StringUtility.trimWhitespace(" "));
        assertEquals("", StringUtility.trimWhitespace("\t"));
        assertEquals("a", StringUtility.trimWhitespace(" a"));
        assertEquals("a", StringUtility.trimWhitespace("a "));
        assertEquals("a", StringUtility.trimWhitespace(" a "));
        assertEquals("a b", StringUtility.trimWhitespace(" a b "));
        assertEquals("a b  c", StringUtility.trimWhitespace(" a b  c "));
    }

    @Test
    public void testTrimAllWhitespace() {
        assertEquals("", StringUtility.trimAllWhitespace(""));
        assertEquals("", StringUtility.trimAllWhitespace(" "));
        assertEquals("", StringUtility.trimAllWhitespace("\t"));
        assertEquals("a", StringUtility.trimAllWhitespace(" a"));
        assertEquals("a", StringUtility.trimAllWhitespace("a "));
        assertEquals("a", StringUtility.trimAllWhitespace(" a "));
        assertEquals("ab", StringUtility.trimAllWhitespace(" a b "));
        assertEquals("abc", StringUtility.trimAllWhitespace(" a b  c "));
    }

    @Test
    public void testTrimLeadingWhitespace() {
        assertEquals(null, StringUtility.trimLeadingWhitespace(null));
        assertEquals("", StringUtility.trimLeadingWhitespace(""));
        assertEquals("", StringUtility.trimLeadingWhitespace(" "));
        assertEquals("", StringUtility.trimLeadingWhitespace("\t"));
        assertEquals("a", StringUtility.trimLeadingWhitespace(" a"));
        assertEquals("a ", StringUtility.trimLeadingWhitespace("a "));
        assertEquals("a ", StringUtility.trimLeadingWhitespace(" a "));
        assertEquals("a b ", StringUtility.trimLeadingWhitespace(" a b "));
        assertEquals("a b  c ", StringUtility.trimLeadingWhitespace(" a b  c "));
    }

    @Test
    public void testTrimLeadingCharacter() {
        assertEquals(null, StringUtility.trimLeadingCharacter(null, ' '));
        assertEquals("", StringUtility.trimLeadingCharacter("", ' '));
        assertEquals("", StringUtility.trimLeadingCharacter(" ", ' '));
        assertEquals("\t", StringUtility.trimLeadingCharacter("\t", ' '));
        assertEquals("a", StringUtility.trimLeadingCharacter(" a", ' '));
        assertEquals("a ", StringUtility.trimLeadingCharacter("a ", ' '));
        assertEquals("a ", StringUtility.trimLeadingCharacter(" a ", ' '));
        assertEquals("a b ", StringUtility.trimLeadingCharacter(" a b ", ' '));
        assertEquals("a b  c ", StringUtility.trimLeadingCharacter(" a b  c ", ' '));
    }

    @Test
    public void testTrimTrailingCharacter() {
        assertEquals(null, StringUtility.trimTrailingCharacter(null, ' '));
        assertEquals("", StringUtility.trimTrailingCharacter("", ' '));
        assertEquals("", StringUtility.trimTrailingCharacter(" ", ' '));
        assertEquals("\t", StringUtility.trimTrailingCharacter("\t", ' '));
        assertEquals("a", StringUtility.trimTrailingCharacter("a ", ' '));
        assertEquals(" a", StringUtility.trimTrailingCharacter(" a", ' '));
        assertEquals(" a", StringUtility.trimTrailingCharacter(" a ", ' '));
        assertEquals(" a b", StringUtility.trimTrailingCharacter(" a b ", ' '));
        assertEquals(" a b  c", StringUtility.trimTrailingCharacter(" a b  c ", ' '));
    }

    @Test
    public void testStartsWithIgnoreCase() {
        String prefix = "fOo";
        assertTrue(StringUtility.startsWithIgnoreCase("foo", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("Foo", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("foobar", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("foobarbar", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("Foobar", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("FoobarBar", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("foObar", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("FOObar", prefix));
        assertTrue(StringUtility.startsWithIgnoreCase("fOobar", prefix));
        assertFalse(StringUtility.startsWithIgnoreCase(null, prefix));
        assertFalse(StringUtility.startsWithIgnoreCase("fOobar", null));
        assertFalse(StringUtility.startsWithIgnoreCase("b", prefix));
        assertFalse(StringUtility.startsWithIgnoreCase("barfoo", prefix));
        assertFalse(StringUtility.startsWithIgnoreCase("barfoobar", prefix));
    }

    @Test
    public void testQuote() {
        assertEquals("'myString'", StringUtility.quote("myString"));
        assertEquals("''", StringUtility.quote(""));
        assertNull(StringUtility.quote(null));
    }

    @Test
    public void testQuoteIfString() {
        assertEquals("'myString'", StringUtility.quoteIfString("myString"));
        assertEquals("''", StringUtility.quoteIfString(""));
        assertEquals(Integer.valueOf(5), StringUtility.quoteIfString(5));
        assertNull(StringUtility.quoteIfString(null));
    }

    @Test
    public void testIsAlpha() {
        assertFalse(StringUtility.isAlpha(null));
        assertFalse(StringUtility.isAlpha(""));
        assertFalse(StringUtility.isAlpha(" "));
        assertTrue(StringUtility.isAlpha("a"));
        assertTrue(StringUtility.isAlpha("A"));
        assertTrue(StringUtility.isAlpha("kgKgKgKgkgkGkjkjlJlOKLgHdGdHgl"));
        assertFalse(StringUtility.isAlpha("ham kso"));
        assertFalse(StringUtility.isAlpha("1"));
        assertFalse(StringUtility.isAlpha("hkHKHik6iUGHKJgU7tUJgKJGI87GIkug"));
        assertFalse(StringUtility.isAlpha("_"));
        assertFalse(StringUtility.isAlpha("hkHKHik*khbkuh"));
    }

    @Test
    public void testIsAlphanumeric() {
        assertFalse(StringUtility.isAlphanumeric(null));
        assertFalse(StringUtility.isAlphanumeric(""));
        assertFalse(StringUtility.isAlphanumeric(" "));
        assertTrue(StringUtility.isAlphanumeric("a"));
        assertTrue(StringUtility.isAlphanumeric("A"));
        assertTrue(StringUtility.isAlphanumeric("kgKgKgKgkgkGkjkjlJlOKLgHdGdHgl"));
        assertFalse(StringUtility.isAlphanumeric("ham kso"));
        assertTrue(StringUtility.isAlphanumeric("1"));
        assertTrue(StringUtility.isAlphanumeric("hkHKHik6iUGHKJgU7tUJgKJGI87GIkug"));
        assertFalse(StringUtility.isAlphanumeric("_"));
        assertFalse(StringUtility.isAlphanumeric("hkHKHik*khbkuh"));
    }

    @Test
    public void testIsWhitespace() {
        assertFalse(StringUtility.isWhitespace(null));
        assertTrue(StringUtility.isWhitespace(""));
        assertTrue(StringUtility.isWhitespace(" "));
        assertTrue(StringUtility.isWhitespace("\t \n \t"));
        assertFalse(StringUtility.isWhitespace("\t aa\n \t"));
        assertTrue(StringUtility.isWhitespace(" "));
        assertFalse(StringUtility.isWhitespace(" a "));
        assertFalse(StringUtility.isWhitespace("a  "));
        assertFalse(StringUtility.isWhitespace("  a"));
        assertFalse(StringUtility.isWhitespace("aba"));
        assertTrue(StringUtility.isWhitespace(" "));
    }

    @Test
    public void testIsAlphaspace() {
        assertFalse(StringUtility.isAlphaSpace(null));
        assertTrue(StringUtility.isAlphaSpace(""));
        assertTrue(StringUtility.isAlphaSpace(" "));
        assertTrue(StringUtility.isAlphaSpace("a"));
        assertTrue(StringUtility.isAlphaSpace("A"));
        assertTrue(StringUtility.isAlphaSpace("kgKgKgKgkgkGkjkjlJlOKLgHdGdHgl"));
        assertTrue(StringUtility.isAlphaSpace("ham kso"));
        assertFalse(StringUtility.isAlphaSpace("1"));
        assertFalse(StringUtility.isAlphaSpace("hkHKHik6iUGHKJgU7tUJgKJGI87GIkug"));
        assertFalse(StringUtility.isAlphaSpace("_"));
        assertFalse(StringUtility.isAlphaSpace("hkHKHik*khbkuh"));
    }

    @Test
    public void testIsAlphanumericSpace() {
        assertFalse(StringUtility.isAlphanumericSpace(null));
        assertTrue(StringUtility.isAlphanumericSpace(""));
        assertTrue(StringUtility.isAlphanumericSpace(" "));
        assertTrue(StringUtility.isAlphanumericSpace("a"));
        assertTrue(StringUtility.isAlphanumericSpace("A"));
        assertTrue(StringUtility.isAlphanumericSpace("kgKgKgKgkgkGkjkjlJlOKLgHdGdHgl"));
        assertTrue(StringUtility.isAlphanumericSpace("ham kso"));
        assertTrue(StringUtility.isAlphanumericSpace("1"));
        assertTrue(StringUtility.isAlphanumericSpace("hkHKHik6iUGHKJgU7tUJgKJGI87GIkug"));
        assertFalse(StringUtility.isAlphanumericSpace("_"));
        assertFalse(StringUtility.isAlphanumericSpace("hkHKHik*khbkuh"));
    }

    @Test
    public void testIsNumeric() {
        assertFalse(StringUtility.isNumeric(null));
        assertFalse(StringUtility.isNumeric(""));
        assertFalse(StringUtility.isNumeric(" "));
        assertFalse(StringUtility.isNumeric("a"));
        assertFalse(StringUtility.isNumeric("A"));
        assertFalse(StringUtility.isNumeric("kgKgKgKgkgkGkjkjlJlOKLgHdGdHgl"));
        assertFalse(StringUtility.isNumeric("ham kso"));
        assertTrue(StringUtility.isNumeric("1"));
        assertTrue(StringUtility.isNumeric("1000"));
        assertTrue(StringUtility.isNumeric("\u0967\u0968\u0969"));
        assertFalse(StringUtility.isNumeric("\u0967\u0968 \u0969"));
        assertFalse(StringUtility.isNumeric("2.3"));
        assertFalse(StringUtility.isNumeric("10 00"));
        assertFalse(StringUtility.isNumeric("hkHKHik6iUGHKJgU7tUJgKJGI87GIkug"));
        assertFalse(StringUtility.isNumeric("_"));
        assertFalse(StringUtility.isNumeric("hkHKHik*khbkuh"));
        assertFalse(StringUtility.isNumeric("+123"));
        assertFalse(StringUtility.isNumeric("-123"));
    }

    @Test
    public void testIsNumericSpace() {
        assertFalse(StringUtility.isNumericSpace(null));
        assertTrue(StringUtility.isNumericSpace(""));
        assertTrue(StringUtility.isNumericSpace(" "));
        assertFalse(StringUtility.isNumericSpace("a"));
        assertFalse(StringUtility.isNumericSpace("A"));
        assertFalse(StringUtility.isNumericSpace("kgKgKgKgkgkGkjkjlJlOKLgHdGdHgl"));
        assertFalse(StringUtility.isNumericSpace("ham kso"));
        assertTrue(StringUtility.isNumericSpace("1"));
        assertTrue(StringUtility.isNumericSpace("1000"));
        assertFalse(StringUtility.isNumericSpace("2.3"));
        assertTrue(StringUtility.isNumericSpace("10 00"));
        assertTrue(StringUtility.isNumericSpace("\u0967\u0968\u0969"));
        assertTrue(StringUtility.isNumericSpace("\u0967\u0968 \u0969"));
        assertFalse(StringUtility.isNumericSpace("hkHKHik6iUGHKJgU7tUJgKJGI87GIkug"));
        assertFalse(StringUtility.isNumericSpace("_"));
        assertFalse(StringUtility.isNumericSpace("hkHKHik*khbkuh"));
    }
}

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