Boxing - from k&b

[Meena R. Krishnan]

From K&B, pg: 258:

Using == with wrappers is tricky; wrappers with the same small values (typically lower than 127), will be == , larger values will not be ==.

but, it is not the case

Integer i9 = new Integer(100);
Integer i10 = new Integer(100);
System.out.println("(small values) " + (i9==i10));//false


Integer i11 = new Integer(1000);
Integer i12 = new Integer(1000);
System.out.println("(large values) " + (i11==i10));//false

both return false.

[Chandra Bhatt]

This is the case when both references refer to the objects created using
autoboxing instead of using new operator.

Integer i1=100; //autoboxed
Integer i2=100; //autoboxed


(i1==i2)//true


That is play of words as you refer to the lines of K&B.

Using new operator to create object means a new object will be created
on the heap and its reference is assigned to the ref variable. Each time
new is used, new object is created and consequently new reference is
returned.




Thanks,
[ May 24, 2007: Message edited by: Chandra Bhatt ]

[Henry Wong]

From your subject header, you imply that K&B is discussing autoboxing. But in your example, which is intended to prove K&B wrong, you don't use anying autoboxing.

Basically, those statements in K&B is true if all the objects were achieved by autoboxing. If you create two different objects explicitedly, those two different objects will be... well... two different objects.

Henry