How to make loop infinite with “x <= y && x >= y && x != y”?

Question

I had this interview question some years ago but I haven\'t found the answer yet.

What should be x and y to make a infinite loop?

while (x <= y&am         


        

Answer 1

you have to create two Integer Objects, for example:

Integer x = new Integer(2);
Integer y = new Integer(2);

Because x and y are Objects and no ordinal types, you get an infinite loop.

Answer 2

Here it is.

Integer x =1;
Integer y = new Integer(1);
while(x <= y&& x >= y && x != y) {
    System.out.println("Success");
}

Answer 3

You've got your answer, I just wanted to say how I got to the same one. In the normal world such a test would be useless, there is no way for two number to work like that. So that means it HAS to be some java specific.

x and y could be either simple types - which makes it impossible right away.

x and y could be objects. But what objects are compared with <= or >=? Only 'boxed' numbers. Thus the answer comes up really fast.

Answer 4

You need two variables which are comparable, have the same value, but represent different instances, for example:

Integer x = new Integer(0);
Integer y = new Integer(0);

x <= y and y <= x are both true because the Integer are unboxed, however the instance equality x == y is false.

Note that it works with Float, Long and Double too, and any value (not just 0) works.

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You can also play with the intricacies of your JVM - they generally cache integer up to 127 only, so this would work too:

Integer x = 128;
Integer y = 128;

(but it would not with 127).

Or more simply, since Doubles are generally not cached at all:

Double x = 0d;
Double y = 0d;