Wrappers question

[Natallia Bahlai]

   Boolean b1 = new Boolean(true);
	  Boolean b2 = new Boolean("true");
	  boolean b3 = b1; 
	  System.out.println(b1 == b2);
	  System.out.println(b2 == b3);
	  System.out.println(b1 == b3);  

Why b2 == b3 results true while b1 == b2 return false?

Thanks in advance.

[Natallia Bahlai]

The second question is

   Integer i1 = new Integer(10);
	  int i2 = i1;
	  Integer i3 = i2;
	  Integer i4 = i2;
	  
	  System.out.println(i1 == i2);
	  System.out.println(i3 == i2);
	  System.out.println(i1 == i3);  

Why i1 == i3 returns false?

[Leonardo Carreira]

    
Boolean b1 = new Boolean(true);
Boolean b2 = new Boolean("true");
boolean b3 = b1; 

System.out.println(b1 == b2);
System.out.println(b2 == b3);
System.out.println(b1 == b3);

Result :
false
true
true

b1==b2 results false because it checks the same object in memory, especially checks the same object's id in memory..

[Natallia Bahlai]

And what happens when I compare b2 == b3, boxing or unboxing occurs?

Thanks.

[Bupjae Lee]

b2 will unbox from Boolean to boolean, and compare unboxed value with value of b3

[Leonardo Carreira]

Natallia Bahlai wrote:And what happens when I compare b2 == b3, boxing or unboxing occurs?
.

i think it is done implicitly by compiler, because either boxing or unboxing occurs will give the same result...

   
Boolean b2 = new Boolean("true");
boolean b4 =b2;     //this is unboxing.. b4 variable is used to accomodate b2 unboxing value

System.out.println(b2 == b4);

Result : true

   
Boolean b1 = new Boolean(true);
boolean b3 = b1; 
Boolean b5 = b3;  //this is boxing.. b5 variable is used to accomodate b3 boxing value

System.out.println(b3 == b5);

Result : true

[Purvesh Maheshwari]

Natallia Bahlai wrote:The second question is

   Integer i1 = new Integer(10);
	  int i2 = i1;
	  Integer i3 = i2;
	  Integer i4 = i2;
	  
	  System.out.println(i1 == i2);
	  System.out.println(i3 == i2);
	  System.out.println(i1 == i3);  

Why i1 == i3 returns false?

When AUTO-Boxing done at line Integer i3=i2,new object implicitly generated and the int value is assigned to new object.when you trying to compare two different object using == then it will return false.

Also AUTO-Unboxing will be done while comparing one primitive type with object of respective wrapper class.
But NO AUTO (UNBOXING OR BOXING) operation happen while comparing two object using == operate.

Hope this will help you Natallia.

[Natallia Bahlai]

Thanks for clarifications!