Integer Wrapper Class in Java

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The Integer class in Java is a wrapper class for the primitive data type int. It is part of the java.lang package and provides various methods to work with integers, such as parsing, converting, and comparing them. The Integer class also provides constants and static methods for integer operations.

Key Features of Integer Wrapper Class

1. Immutability: Instances of the Integer class are immutable.
2. Constants: Provides constants like MIN_VALUE and MAX_VALUE.
3. Static Methods: Methods for parsing strings to integers, comparing integers, and converting integers to strings.

Integer Class Methods

Here are some commonly used methods in the Integer class:

1. int intValue()
2. static int compare(int x, int y)
3. boolean equals(Object obj)
4. static int parseInt(String s)
5. static int parseInt(String s, int radix)
6. String toString()
7. static String toString(int i)
8. static Integer valueOf(int i)
9. static Integer valueOf(String s)
10. static Integer valueOf(String s, int radix)
11. static int sum(int a, int b)

1. int intValue()

Returns the value of this Integer as an int.

public class IntegerExample {
    public static void main(String[] args) {
        Integer i = Integer.valueOf(10);
        int value = i.intValue();
        System.out.println(value);  // Output: 10
    }
}

Output:

10

2. static int compare(int x, int y)

Compares two int values numerically.

public class IntegerExample {
    public static void main(String[] args) {
        System.out.println(Integer.compare(10, 20));  // Output: -1
    }
}

Output:

-1

3. boolean equals(Object obj)

Compares this object to the specified object.

public class IntegerExample {
    public static void main(String[] args) {
        Integer i1 = Integer.valueOf(10);
        Integer i2 = Integer.valueOf(10);
        System.out.println(i1.equals(i2));  // Output: true
    }
}

Output:

true

4. static int parseInt(String s)

Parses the string argument as a signed decimal integer.

public class IntegerExample {
    public static void main(String[] args) {
        int i = Integer.parseInt("123");
        System.out.println(i);  // Output: 123
    }
}

Output:

123

5. static int parseInt(String s, int radix)

Parses the string argument as a signed integer in the radix specified by the second argument.

public class IntegerExample {
    public static void main(String[] args) {
        int i = Integer.parseInt("7B", 16);
        System.out.println(i);  // Output: 123
    }
}

Output:

123

6. String toString()

Returns a string representation of this Integer object.

public class IntegerExample {
    public static void main(String[] args) {
        Integer i = Integer.valueOf(123);
        System.out.println(i.toString());  // Output: "123"
    }
}

Output:

123

7. static String toString(int i)

Returns a string representation of the integer argument.

public class IntegerExample {
    public static void main(String[] args) {
        String s = Integer.toString(123);
        System.out.println(s);  // Output: "123"
    }
}

Output:

123

8. static Integer valueOf(int i)

Returns an Integer instance representing the specified int value.

public class IntegerExample {
    public static void main(String[] args) {
        Integer i = Integer.valueOf(123);
        System.out.println(i);  // Output: 123
    }
}

Output:

123

9. static Integer valueOf(String s)

Returns an Integer object holding the value of the specified String.

public class IntegerExample {
    public static void main(String[] args) {
        Integer i = Integer.valueOf("123");
        System.out.println(i);  // Output: 123
    }
}

Output:

123

10. 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.

public class IntegerExample {
    public static void main(String[] args) {
        Integer i = Integer.valueOf("7B", 16);
        System.out.println(i);  // Output: 123
    }
}

Output:

123

11. static int sum(int a, int b)

Adds two integers together as per the + operator.

public class IntegerExample {
    public static void main(String[] args) {
        int sum = Integer.sum(10, 20);
        System.out.println(sum);  // Output: 30
    }
}

Output:

30

Conclusion

The Integer class in Java provides a wide range of methods for manipulating and converting integer values. Understanding and utilizing these methods can greatly enhance your ability to handle integer operations in your applications. The immutability of the Integer class ensures that instances remain unchanged, providing a reliable and consistent way to work with integers in Java.