Java autoboxing unboxing

Introduction

Encapsulating a value within an object is called boxing.

Extracting a value from a type wrapper is called unboxing. 

Integer iOb = new Integer(100); //box
int i = iOb.intValue(); //unbox

The following code demonstrates box and unbox.

It uses a numeric type wrapper to encapsulate a value and then extract that value. 

public class Main { 
  public static void main(String args[]) { 
     //from www .j  a v  a 2 s  .co m
    Integer iOb = new Integer(100);  
 
    int i = iOb.intValue(); 
 
    System.out.println(i + " " + iOb); // displays 100 100 
  } 
}

Autoboxing happens when a primitive type is automatically encapsulated into its equivalent type wrapper.

Auto-unboxing happens when the value of a boxed object is automatically extracted when its value is needed. 

Integer iOb = 100; // autobox an int 
int i = iOb; // auto-unbox

Here is the preceding program rewritten to use autoboxing/unboxing: 

// Demonstrate autoboxing/unboxing.  
public class Main {  
  public static void main(String args[]) {  
  
    Integer iOb = 100; // autobox an int  
  
    int i = iOb; // auto-unbox  
  
    System.out.println(i + " " + iOb);  // displays 100 100  
  }  /*from   w  ww .  j  ava2 s.c  o m*/
}



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