Compound Assignment Operators

Compound assignment operators like +=, -=, *=, /=, %= and post-increment/decrement provide shorthand for updating variable values.

15–25% of exam

Understand It

Ace It

Context

What this topic is and why it exists

Imagine you're keeping a running tally on a whiteboard.

Every time someone scores a point, you don't erase the whole number and rewrite it from scratch — you just add to what's already there.

That's exactly what compound assignment operators do in Java.

Instead of writing `score = score + 10`, you can write `score += 10`.

It's the same operation, just shorter and cleaner.

The computer looks at whatever value `score` already holds, adds 10 to it, and stores the result right back in `score`.

This shorthand works for all the basic math operations: `-=` subtracts, `*=` multiplies, `/=` divides, and `%=` gives you the remainder.

So `x *= 3` triples whatever `x` currently holds.

Think of the operator as a tiny instruction: "take what's there, do this math, and put the answer back."

There's an even lazier shortcut for the most common case — adding or subtracting just one.

Writing `x++` bumps `x` up by one, and `x--` drops it by one.

You'll see these everywhere, especially in loops.

For the AP exam, just remember: always use them *by themselves* on a line, never buried inside another expression.

Keep it simple, and these little operators will save you a surprising amount of typing and reading time.

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