What is the output of the following Java code? int m = 1000; int k = 3000;…

Concept — pre-increment and the empty statement

In Java, ++x is a pre-increment: the variable is updated first, and every comparison inside that same expression uses the already-updated value. A semicolon written immediately after while (condition) is an empty statement, and that empty statement becomes the loop body — so such a loop does no work of its own; it simply keeps re-evaluating its condition until the condition turns false.

Applying it to this program

1. Start with m = 1000 and k = 3000.

2. Before every comparison, ++m raises m by 1 and --k lowers k by 1. Both updates happen inside the same check.

3. So one check moves m and k one step towards each other, and the sum m + k never changes: it stays 1000 + 3000 = 4000.

4. After n checks, m = 1000 + n and k = 3000 - n.

5. The loop repeats while m < k, that is 1000 + n < 3000 - n, which simplifies to 2n < 2000, so n < 1000. The first 999 checks are therefore true.

6. On check number 1000, m = 2000 and k = 2000, and 2000 < 2000 is false, so the loop ends. m has already been raised to 2000 by that very check.

Cross-check

Trace the first two checks and the last one:

k fell by exactly 1000 while m rose by exactly 1000, so both land on 2000 and the sum is still 4000 — the two routes agree.

Result

The empty body changes nothing else, so System.out.println(m) prints 2000.

Note that the semicolon does not stop the loop after a single pass; it only removes the body. The condition on its own keeps the loop running.