Why output is true and false?

Question

public class Test
{
    public static void main(String ar[])
    {
        Integer a = 10;
        Integer b =10;
        Integer c = 145;
        Integer d = 145;
        System.out.println(a==b);
        System.out.println(c==d);
    }
}

This has been around since 2004 when Java 5.0 was introduced. You might expect this has been answered before ;) — Peter Lawrey, Jul 08 '14 at 07:43
@PeterLawrey - answered several times by several different people.. :P — TheLostMind, Jul 08 '14 at 12:49

score 5 · Answer 1 · answered Jul 08 '14 at 06:36

5

Integer class keeps a local cache for values between -128 and 127.. and returns the same object.

    Integer a = 10;
    Integer b =10;
    Integer c = 145;
    Integer d = 145;
    System.out.println(a==b); // so, a and b are references to the same object --> prints true
    System.out.println(c==d);// so, c and d are references to different objects --> returns false
}

answered Jul 08 '14 at 06:36

TheLostMind

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Side note: It's possible to alter the size of this cache using the `-XX:AutoBoxCacheMax=` argument on the HotSpot VM, so it's entirely possible that `c == d` could return `true`. – awksp Jul 08 '14 at 06:39

Why output is true and false?

1 Answers1