What is the reason for this strange Java behavior?

I want to test the '= =' operator on long. This is what I found: the following code:

public static void main(final String[] args) {
    final Long n = 0L;
    final Long m = 0L;
    System.out.println(n + " == " + m + " : " + (n == m));

    final Long a = 127L;
    final Long b = 127L;
    System.out.println(a + " == " + b + " : " + (a == b));

    final Long A = 128L;
    final Long B = 128L;
    System.out.println(A + " == " + B + " : " + (A == B));

    final Long x = -128L;
    final Long y = -128L;
    System.out.println(x + " == " + y + " : " + (x == y));

    final Long X = -129L;
    final Long Y = -129L;
    System.out.println(X + " == " + Y + " : " + (X == Y));
}

Output:

0 == 0 : true
127 == 127 : true
128 == 128 : false
-128 == -128 : true
-129 == -129 : false

The only explanation I can think of is that the JVM stores all long values in [- 128127] in the Perl space and provides their addresses to long and all values outside the above range. It creates a new allocation for each static value, which is encountered in the code

Am I right? Under what circumstances must we pay attention to similar behavior?

PS. I know I should use nullcheck and then use Equals () to compare objects, but I'm curious if anyone knows the answer

edit

After jtahlborn answered who gave me keyword automatic boxing, I found this wonderful article about well documented answer

Solution

This is the result of automatic packing See long valueOf().