Compound Assignment and Increment Operators

Writing count = count + 1 means: read count, add 1, store the result back in count. That is three jobs for one idea, so Java gives you count += 1 as shorthand. Any compound operator (+=, -=, *=, /=, %=) expands the same way: x *= 3 means x = x·3. Java always finishes computing the right side completely, using whatever value x held the instant before the line ran, then stores the new result. Order matters when you chain several lines: each line uses the value left behind by the line before it, so x += 5; x -= 3; x *= 2; applies those steps one at a time, not all at once.

Increment and decrement operators (++, --) are the same shorthand for adding or subtracting exactly 1, but they come in two flavors depending on where you put the operator. Postfix (x++) hands back the current value first, then increments x afterward. Prefix (++x) increments x first, then hands back the new value. Both leave x one higher once the statement ends — the difference only shows up if you use the result in the same statement, like inside a println or another expression.

This matters because Unit 1 is building your sense that every expression collapses to a value before anything gets stored, and these operators are where that collapsing has a visible order. Once you can trace a line like i++ + ++i step by step, you are ready for loops in later units, where ++ and += are the standard way to move a counter forward each pass.