Java Integer

Java Integer: The meaning and difference between int and integer, converting one to another and need of integer when int already existing etc. are discussed clearly with example in Java int vs Integer. It is advised to read this before going further.

Converting String to int (parsing using parseInt())is given in String to int Conversion in Java.

Example on Java Integer. Some more concepts of Integer are discussed here under.

public class Demo
{
  public static void main(String args[])
  {
    System.out.println("Minimum value Integer: " + Integer.MIN_VALUE);   //prints -2147483648
    System.out.println("Maximum value Integer: " + Integer.MAX_VALUE);   //prints 2147483647

    Integer i1 = new Integer(10);
    Integer i2 = new Integer(10);
    Integer i3 = new Integer(20);
    System.out.println(i1 == i2);             // prints false
    System.out.println(i1 == i3);             // prints false

    System.out.println(i1.equals(i2));        // prints true
    System.out.println(i1.equals(i3));        // prints false

    System.out.println(i1*i1);                // prints 100

    String str1 = i1.toString();
    String str2 = String.valueOf(i1);
    System.out.println(str1);                 // prints 10
    System.out.println(str2);                 // prints 10
  }
}

MIN_VALUE and MAX_VALUE are static final variables declared in Java Integer class that prints the minimum and maximum values an Integer object can take.

We cannot do any arithmetic operations on any Java object. But here, i1*i1 prints 100. The reason is i1 is converted back to int with the concept of autoboxing. This works from JDK 1.5 only; earlier versions of JDK up to 1.4 raises compilation error.

For comparison between Java Integer objects (with == and equals()), strings immutability nature concept is used.

String str1 = i1.toString();
String str2 = String.valueOf(i1);

Any object of Java, to convert into String either toString() of Object class or static method valueOf() can be used.

Just like any object of Java, the Java Integer object i1 takes 4 bytes of memory.

Java Integer is a wrapper class.

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byte TO	short	int	long	float	double	char	boolean
short TO	byte	int	long	float	double	char	boolean
int TO	byte	short	long	float	double	char	boolean
float TO	byte	short	int	long	double	char	boolean
double TO	byte	short	int	long	float	char	boolean
char TO	byte	short	int	long	float	double	boolean
boolean TO	byte	short	int	long	float	double	char

String and data type conversions

String TO	byte	short	int	long	float	double	char	boolean
byte	short	int	long	float	double	char	boolean	TO String