AP Computer Science A Standards: Iteration allows for the repeated execution of a block of code. Java provides while loops (best for indefinite iteration when the number of loops is unknown) and for loops (best for definite iteration). A loop typically consists of initialization, a boolean condition that is checked before each iteration, and an update statement. Errors in any of these can lead to off-by-one errors or infinite loops. Variables declared in a for loop header are scoped only to that loop.