# Infinite Loop Puzzles in Java

Problem 1 : Insert code in the given code segments to make the loop infinite.

 `class` `GFG ` `{ ` `      ``public` `static` `void` `main(String s[]){ ` ` `  `           ``/* Insert code here */` ` `  `           ``for` `(``int` `i = start; i <= start + ``1``; i++) { ` ` `  `             ``/* Infinite loop */` `           ``} ` `      ``} ` `} `

Solution:
It looks as though it should run for only two iterations, but it can be made to loop indefinitely by taking advantage of the overflow behavior.
Integer.MAX_VALUE is the maximum value that an int can store in Java. When i gets to Integer.MAX_VALUE and is incremented, it silently wraps around to Integer.MIN_VALUE. So, we can declare variable start with 1 less than maximum value.
Following is the solution:

 `class` `GFG ` `{ ` `      ``public` `static` `void` `main(String s[]){ ` ` `  `           ``int` `start = Integer.MAX_VALUE-``1``; ` `           ``for` `(``int` `i = start; i <= start + ``1``; i++) { ` `             ``/* Infinite loop */` `           ``} ` `      ``} ` `} `

In this, start=2147483645 (Integer.MAX_VALUE-1), and the value goes like 2147483645, 2147483646, -2147483648, -2147483647…….. and so on.

Problem 2 Insert code in the given code segments to make the loop infinite.

 `class` `GFG ` `{ ` `      ``public` `static` `void` `main(String s[]) { ` ` `  `           ``/* Insert code here */` ` `  `           ``while` `(i <= j && j <= i && i != j) { ` ` `  `            ``/* Infinite loop */` ` `  `           ``} ` `      ``} ` `} `

Solution:
Until release 5.0, Javaâ€™s numerical comparison operators (=) required both of their operands to be of a primitive numeric type (byte, char, short, int, long, float, or double). In release 5.0, the specification was changed to say that the type of each operand must be convertible to a primitive numeric type. Therein lies the rub.
In release 5.0, autoboxing and auto-unboxing were added to the language. We are using this in the following :

 `class` `GFG ` `{ ` `      ``public` `static` `void` `main(String s[]){ ` `          ``Integer i = ``new` `Integer(``0``); ` `          ``Integer j = ``new` `Integer(``0``); ` `           ``while` `(i <= j && j <= i && i != j) { ` `            ``/* Infinite loop */` `           ``} ` `      ``} ` `} `

The first two subexpressions (i <= j and j <= i) perform unboxing conversions on i and j and compare the resulting int values numerically. Both i and j represent 0, so both of these subexpressions evaluate to true. The third subexpression (i != j) performs an identity comparison on the object references i and j. The two variables refer to distinct objects, as each was initialized to a new Integer instance. Therefore, the third subexpression also evaluates to true, and the loop spins forever.

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