QA. Object pooling of Java wrappers

Scenario

class Demo {

  public static void main(String[] args) {

     Integer i = 100;

     Integer j = 100;

     System.out.println(i==j);

     Integer x = 127;

     Integer y = 127;

     System.out.println(x==y);

     Integer a = 128;

     Integer b = 128;

     System.out.println(a==b);

  

     Integer p = 100;

     Integer q = new Integer(100);

     System.out.println(p==q);     

  }

}

What value will be printed ?

Result

truetrue

false

false

Explanation

Wrappers are used from Object pool if value being boxed is :

• true or false
• A byte
• A char in the range \u0000 to \u007f
• An int or short number between -128 and 127 (inclusive)

Wrapper object created using new operator will always use separate memory in heap and will not pick pooled objects.