Why the output is True False for the following code

Question

Integer i1 = 127;
Integer i2 = 127;
System.out.println(i1 == i2);
i1 = 128;
i2 = 128;
System.out.println(i1 == i2);

Answer 1

Basically, it is an optimization to save memory.
On your IDE inside Integer class see IntegerCache static nested class, there you will find how is this implemented.
Here you will find detailed explanations:

https://stackoverflow.com/questions/3131136/integers-caching-in-java

https://dzone.com/articles/java-integer-cache-why-integervalueof127-integerva

https://stackoverflow.com/questions/20897020/why-integer-class-caching-values-in-the-range-128-to-127

Answer 2

Thankyou voja

Answer 3

Warning: A pure speculation.

It seems when <i1> and <i2> are assigned a new value, a new object is created for each these variables, and then, having each their own object, the == operator returns False. Because the variables <i1> and <i2> no longer reference to the same object.

System.identityHashCode(i1) differs to System.identityHashCode(i2). After the new value assignment.

However, I read in below discussion, System.identityHashCode() isn't something we should rely on for comparison of objects. This is not something comparable to the `address of` & operator in C/C++ I suppose.

https://stackoverflow.com/a/1961150

Hth, cmiiw

Answer 4

so compare it with
i1.equals(i2)