Integer Wrapper Class in Java

The Integer class wraps a value of the primitive type int in an object. An object of type Integer contains a single field whose type is int.

In addition, this class provides several methods for converting an int to a String and a String to an int, as well as other constants and methods useful when dealing with an int.

Integer class Constructors

• Integer(int value) - Constructs a newly allocated Integer object that represents the specified int value.
• Integer(String s) - Constructs a newly allocated Integer object that represents the int value indicated by the String parameter.

Example:

int b = 55;
String str= "45";
// Construct two Integer objects
Integer x = new Integer(b);
Integer y = new Integer(str);

Integer class Methods

A diagram shows a list of APIs/Methods that Integer class provides.

In this post, we will learn a few important methods of the Integer wrapper class provides.

toString() methods

• String toString() - Returns a String object representing this Integer's value.
• static String toString(int i) - Returns a String object representing the specified integer.
• static String toString(int i, int radix) - Returns a string representation of the first argument in the radix specified by the second argument.

Example: Example to demonstrate above all toString() methods.

private static void toStringMethods() {
 // toString()
 System.out.println("toString(b) = " + Integer.toString(b));

 // toHexString(),toOctalString(),toBinaryString()
 // converts into hexadecimal, octal and binary forms.
 System.out.println("toHexString(b) =" + Integer.toHexString(b));
 System.out.println("toOctalString(b) =" + Integer.toOctalString(b));
 System.out.println("toBinaryString(b) =" + Integer.toBinaryString(b));

}

Output:

toString(b) = 55
toHexString(b) =37
toOctalString(b) =67
toBinaryString(b) =110111

valueOf() Methods

• static Integer valueOf(int i) - Returns an Integer instance representing the specified int value.
• static Integer valueOf(String s) - Returns an Integer object holding the value of the specified String.
• static Integer valueOf(String s, int radix) - Returns an Integer object holding the value extracted from the specified String when parsed with the radix given by the second argument.

Example:

private static void valueOfMethods() {
 // valueOf(): return Integer object
 // an overloaded method takes radix as well.
 Integer z = Integer.valueOf(b);
 System.out.println("valueOf(b) = " + z);
 z = Integer.valueOf(bb);
 System.out.println("ValueOf(bb) = " + z);
 z = Integer.valueOf(bb, 6);
 System.out.println("ValueOf(bb,6) = " + z);

}

Output:

valueOf(b) = 55
ValueOf(bb) = 45
ValueOf(bb,6) = 29

parseInt() methods

• static int parseInt(String s) - Parses the string argument as a signed decimal integer.
• static int parseInt(String s, int radix) - Parses the string argument as a signed integer in the radix specified by the second argument.

Example:

private static void parseIntMethods() {
 // parseInt(): return primitive int value
 // an overloaded method takes radix as well
 int zz = Integer.parseInt(bb);
 System.out.println("parseInt(bb) = " + zz);
 zz = Integer.parseInt(bb, 6);
 System.out.println("parseInt(bb,6) = " + zz);

}

Output:

parseInt(bb) = 45
parseInt(bb,6) = 29

rotateLeft() and rotateRight() methods

• static int rotateLeft(int i, int distance) - Returns the value obtained by rotating the two's complement binary representation of the specified int value left by the specified number of bits.
• static int rotateRight(int i, int distance) - Returns the value obtained by rotating the two's complement binary representation of the specified int value right by the specified number of bits.

Example:

private static void rotateMethods() {
 // rotateLeft and rotateRight can be used
 // to rotate bits by specified distance
 int valrot = 2;
 System.out.println("rotateLeft(0000 0000 0000 0010 , 2) =" + Integer.rotateLeft(valrot, 2));
 System.out.println("rotateRight(0000 0000 0000 0010,3) =" + Integer.rotateRight(valrot, 3));
}

Output:

rotateLeft(0000 0000 0000 0010 , 2) =8
rotateRight(0000 0000 0000 0010,3) =1073741824

decode() method

• static Integer decode(String nm) - Decodes a String into an Integer.

Example:

private static void decodeMethods() {

 // decode() : decodes the hex,octal and decimal
 // string to corresponding int values.
 String decimal = "45";
 String octal = "005";
 String hex = "0x0f";
 Integer dec = Integer.decode(decimal);
 System.out.println("decode(45) = " + dec);
 dec = Integer.decode(octal);
 System.out.println("decode(005) = " + dec);
 dec = Integer.decode(hex);
 System.out.println("decode(0x0f) = " + dec);

}

Output:

decode(45) = 45
decode(005) = 5
decode(0x0f) = 15

getInteger() methods

• static Integer getInteger(String nm) - Determines the integer value of the system property with the specified name.
• static Integer getInteger(String nm, int val) - Determines the integer value of the system property with the specified name.
• static Integer getInteger(String nm, Integer val) - Returns the integer value of the system property with the specified name.

Example:

private static void getIntegerMethods() {
 // getInteger(): can be used to retrieve
 // int value of system property
 int prop = Integer.getInteger("sun.arch.data.model");
 System.out.println("getInteger(sun.arch.data.model) = " + prop);
 System.out.println("getInteger(abcd) =" + Integer.getInteger("abcd"));

 // an overloaded getInteger() method
 // which return default value if property not found.
 System.out.println("getInteger(abcd,10) =" + Integer.getInteger("abcd", 10));

}

Output:

getInteger(sun.arch.data.model) = 64
getInteger(abcd) =null
getInteger(abcd,10) =10

int,byte,short,long,double,float value() methods

private static void valueMethods() {
 // Construct two Integer objects
 Integer x = new Integer(b);
 // xxxValue can be used to retrieve
 // xxx type value from int value.
 // xxx can be int,byte,short,long,double,float
 System.out.println("bytevalue(x) = " + x.byteValue());
 System.out.println("shortvalue(x) = " + x.shortValue());
 System.out.println("intvalue(x) = " + x.intValue());
 System.out.println("longvalue(x) = " + x.longValue());
 System.out.println("doublevalue(x) = " + x.doubleValue());
 System.out.println("floatvalue(x) = " + x.floatValue());
}

Output:

bytevalue(x) = 55
shortvalue(x) = 55
intvalue(x) = 55
longvalue(x) = 55
doublevalue(x) = 55.0
floatvalue(x) = 55.0

bitcount()

int value = 45;

// bitcount() : can be used to count set bits
// in twos complement form of the number
System.out.println("Integer.bitcount(value)=" + Integer.bitCount(value));

numberOfTrailingZeros() and numberOfLeadingZeros() methods

// numberOfTrailingZeroes and numberOfLeaadingZeroes
// can be used to count prefix and postfix sequence of 0
System.out.println("Integer.numberOfTrailingZeros(value)=" + Integer.numberOfTrailingZeros(value));
System.out.println("Integer.numberOfLeadingZeros(value)=" + Integer.numberOfLeadingZeros(value));

highestOneBit() method

// highestOneBit returns a value with one on highest
// set bit position
System.out.println("Integer.highestOneBit(value)=" + Integer.highestOneBit(value));

lowestOneBit() method

// highestOneBit returns a value with one on lowest
// set bit position
System.out.println("Integer.lowestOneBit(value)=" + Integer.lowestOneBit(value));

reverse() and reverseytes() methods

// reverse() can be used to reverse order of bits
// reverseytes() can be used to reverse order of bytes
System.out.println("Integer.reverse(value)=" + Integer.reverse(value));
System.out.println("Integer.reverseBytes(value)=" + Integer.reverseBytes(value));

signum() method

// signum() returns -1,0,1 for negative,0 and positive
// values
System.out.println("Integer.signum(value)=" + Integer.signum(value));

hashcode(), equals(), compare() and compareTo() methods

// hashcode() returns hashcode of the object
int hash = x.hashCode();
System.out.println("hashcode(x) = " + hash);

// equals returns boolean value representing equality
boolean eq = x.equals(y);
System.out.println("x.equals(y) = " + eq);

// compare() used for comparing two int values
int e = Integer.compare(x, y);
System.out.println("compare(x,y) = " + e);

// compareTo() used for comparing this value with some
// other value
int f = x.compareTo(y);
System.out.println("x.compareTo(y) = " + f);

Complete Program for Reference

package com.javaguides.corejava.wrapperclasses;

/**
 * 
 * @author javaguides.net
 *
 */
public class IntegerClassExample {

 static int b = 55;
 static String bb = "45";

 private static void toStringMethods() {
  // toString()
  System.out.println("toString(b) = " + Integer.toString(b));

  // toHexString(),toOctalString(),toBinaryString()
  // converts into hexadecimal, octal and binary forms.
  System.out.println("toHexString(b) =" + Integer.toHexString(b));
  System.out.println("toOctalString(b) =" + Integer.toOctalString(b));
  System.out.println("toBinaryString(b) =" + Integer.toBinaryString(b));

 }

 private static void valueOfMethods() {
  // valueOf(): return Integer object
  // an overloaded method takes radix as well.
  Integer z = Integer.valueOf(b);
  System.out.println("valueOf(b) = " + z);
  z = Integer.valueOf(bb);
  System.out.println("ValueOf(bb) = " + z);
  z = Integer.valueOf(bb, 6);
  System.out.println("ValueOf(bb,6) = " + z);

 }

 private static void parseIntMethods() {
  // parseInt(): return primitive int value
  // an overloaded method takes radix as well
  int zz = Integer.parseInt(bb);
  System.out.println("parseInt(bb) = " + zz);
  zz = Integer.parseInt(bb, 6);
  System.out.println("parseInt(bb,6) = " + zz);

 }

 private static void getIntegerMethods() {
  // getInteger(): can be used to retrieve
  // int value of system property
  int prop = Integer.getInteger("sun.arch.data.model");
  System.out.println("getInteger(sun.arch.data.model) = " + prop);
  System.out.println("getInteger(abcd) =" + Integer.getInteger("abcd"));

  // an overloaded getInteger() method
  // which return default value if property not found.
  System.out.println("getInteger(abcd,10) =" + Integer.getInteger("abcd", 10));

 }

 private static void decodeMethods() {

  // decode() : decodes the hex,octal and decimal
  // string to corresponding int values.
  String decimal = "45";
  String octal = "005";
  String hex = "0x0f";
  Integer dec = Integer.decode(decimal);
  System.out.println("decode(45) = " + dec);
  dec = Integer.decode(octal);
  System.out.println("decode(005) = " + dec);
  dec = Integer.decode(hex);
  System.out.println("decode(0x0f) = " + dec);

 }

 private static void rotateMethods() {
  // rotateLeft and rotateRight can be used
  // to rotate bits by specified distance
  int valrot = 2;
  System.out.println("rotateLeft(0000 0000 0000 0010 , 2) =" + Integer.rotateLeft(valrot, 2));
  System.out.println("rotateRight(0000 0000 0000 0010,3) =" + Integer.rotateRight(valrot, 3));
 }

 private static void valueMethods() {
  // Construct two Integer objects
  Integer x = new Integer(b);
  // xxxValue can be used to retrieve
  // xxx type value from int value.
  // xxx can be int,byte,short,long,double,float
  System.out.println("bytevalue(x) = " + x.byteValue());
  System.out.println("shortvalue(x) = " + x.shortValue());
  System.out.println("intvalue(x) = " + x.intValue());
  System.out.println("longvalue(x) = " + x.longValue());
  System.out.println("doublevalue(x) = " + x.doubleValue());
  System.out.println("floatvalue(x) = " + x.floatValue());
 }

 public static void main(String[] args) {

  // Construct two Integer objects
  Integer x = new Integer(b);
  Integer y = new Integer(bb);

  toStringMethods();
  parseIntMethods();
  rotateMethods();
  toStringMethods();
  valueOfMethods();
  decodeMethods();
  getIntegerMethods();
  valueMethods();
  
  
  int value = 45;

  // bitcount() : can be used to count set bits
  // in twos complement form of the number
  System.out.println("Integer.bitcount(value)=" + Integer.bitCount(value));

  // numberOfTrailingZeroes and numberOfLeaadingZeroes
  // can be used to count prefix and postfix sequence of 0
  System.out.println("Integer.numberOfTrailingZeros(value)=" + Integer.numberOfTrailingZeros(value));
  System.out.println("Integer.numberOfLeadingZeros(value)=" + Integer.numberOfLeadingZeros(value));

  // highestOneBit returns a value with one on highest
  // set bit position
  System.out.println("Integer.highestOneBit(value)=" + Integer.highestOneBit(value));

  // highestOneBit returns a value with one on lowest
  // set bit position
  System.out.println("Integer.lowestOneBit(value)=" + Integer.lowestOneBit(value));

  // reverse() can be used to reverse order of bits
  // reverseytes() can be used to reverse order of bytes
  System.out.println("Integer.reverse(value)=" + Integer.reverse(value));
  System.out.println("Integer.reverseBytes(value)=" + Integer.reverseBytes(value));

  // signum() returns -1,0,1 for negative,0 and positive
  // values
  System.out.println("Integer.signum(value)=" + Integer.signum(value));

  // hashcode() returns hashcode of the object
  int hash = x.hashCode();
  System.out.println("hashcode(x) = " + hash);

  // equals returns boolean value representing equality
  boolean eq = x.equals(y);
  System.out.println("x.equals(y) = " + eq);

  // compare() used for comparing two int values
  int e = Integer.compare(x, y);
  System.out.println("compare(x,y) = " + e);

  // compareTo() used for comparing this value with some
  // other value
  int f = x.compareTo(y);
  System.out.println("x.compareTo(y) = " + f);
 }
}

Output:

toString(b) = 55
toHexString(b) =37
toOctalString(b) =67
toBinaryString(b) =110111
parseInt(bb) = 45
parseInt(bb,6) = 29
rotateLeft(0000 0000 0000 0010 , 2) =8
rotateRight(0000 0000 0000 0010,3) =1073741824
toString(b) = 55
toHexString(b) =37
toOctalString(b) =67
toBinaryString(b) =110111
valueOf(b) = 55
ValueOf(bb) = 45
ValueOf(bb,6) = 29
decode(45) = 45
decode(005) = 5
decode(0x0f) = 15
getInteger(sun.arch.data.model) = 64
getInteger(abcd) =null
getInteger(abcd,10) =10
bytevalue(x) = 55
shortvalue(x) = 55
intvalue(x) = 55
longvalue(x) = 55
doublevalue(x) = 55.0
floatvalue(x) = 55.0
Integer.bitcount(value)=4
Integer.numberOfTrailingZeros(value)=0
Integer.numberOfLeadingZeros(value)=26
Integer.highestOneBit(value)=32
Integer.lowestOneBit(value)=1
Integer.reverse(value)=-1275068416
Integer.reverseBytes(value)=754974720
Integer.signum(value)=1
hashcode(x) = 55
x.equals(y) = false
compare(x,y) = 1
x.compareTo(y) = 1

Reference

https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html

Related Wrapper Classes

1. Integer Wrapper Class in Java
2. Long Wrapper Class in Java
3. Float Wrapper Class in Java
4. Double Wrapper Class in Java
5. Boolean Wrapper Class in Java
6. Short Wrapper Class in Java
7. Byte Wrapper Class in Java
8. Character Wrapper Class in Java