Why is == true for some Integer objects? [duplicate]

Question

Possible Duplicate:
Integer wrapper objects share the same instances only within the value 127?

I have copied the following program snippet from the Khalid Mughal SCJP, but I am unable to
understand the output.

 public class RQ200_60 {
    public static void main(String[] args) {
        Integer i = -10;
        Integer j = -10;
        System.out.print(i==j);         // output: true -- why true?
        System.out.print(i.equals(j));  // output: true
        Integer n = 128;
        Integer m = 128;
        System.out.print(n==m);         // output: false
        System.out.print(n.equals(m));  // output: true
    }
}      

The above program giving output true for the first print statement but it supposed to give false because it is reference comparison with == relational operator. But third print gives false and I don't understand this inconsistency.

Explanations are greatly appreciated!

Answer 1

The answers about caching are correct. However, if you go...

Integer i = new Integer(10);
Integer j = new Integer(10);

...then you avoid the caching and the results will be what you expected.

Answer 2

In the first case, both the objects i and j are pointing to the same cached object. By default, the range between -128 and 127 are cached as Integer Object. We can increase the range using JVM arguments