while, do-while, break & continue

Two loops run on a condition rather than a count.

while checks first, then runs — the body may execute zero times:

int cups = 0;
while (cups < 3) {
    cups++;
}
// cups == 3 here

do-while runs the body first, then checks — the body always executes at least once. The classic shape is a retry loop:

int attempts = 0;
do {
    attempts++;
    // try something
} while (attempts < 3 && !succeeded);

Use while when the answer might already be "done" (draining a queue); use do-while only when the first pass is required by the problem itself (prompt-then-check input). In practice 90% of condition loops are while.

break and continue control the loop from inside:

int found = -1;
for (int i = 0; i < data.length; i++) {
    if (data[i] < 0) {
        continue;            // skip this element, keep looping
    }
    if (data[i] == target) {
        found = i;
        break;               // stop the whole loop
    }
}

break exits the loop immediately; continue jumps to the next iteration. Both are clearest when rare — a loop full of breaks is really a tangled state machine. Note the standard search idiom: carry the answer in a variable declared outside the loop, so it survives the break.

The infinite loop while (true) { ... break; } is legitimate when the exit is in the middle of the body — but the break must be reachable, and you must be able to say in one sentence what eventually makes it run.

Next: loops inside loops, and the accumulator patterns that make loops earn their keep.