`for` loops

BASIC

Note: This page describes the "traditional" for loop; there is also an enhanced for loop.

A for loop is a kind of loop, which is a kind of control statement. It is a loop with the test at the top. The syntax is:

for (initialization; condition; update) {
    statements
}

The initialization is performed first, and only once. After that, the condition is tested and, if true, the statements are executed and the update is performed; then control returns to the condition. In other words, the for loop behaves almost exactly like the following while loop:

initialization;
while (condition) {
    statements;
    update;
}

There is nothing unusual about the condition or the statements.

The initialization may have one of the following forms:

Assignment to a previously declared variable, for example i = 0;
Declaration and initialization of a variable, for example int i = 0; -- in this case, the scope of the variable is the for statement, and the variable cannot be used outside the loop.
Declaration and initialization of more than one variable, separated by commas, for example int i = 0, j = 0; (this form is rarely used).

The update is one of:

An expression, often i++ or something similar.
A comma-separated list of expressions, such as i++, j += 2 (an assignment statement can be used as an expression).

The braces indicate a block of statements. If there is only one statement, the braces may be omitted; however, it is good style to always include the braces.

For example, the contents of an array a can be written out on a single line by:

for (int i = 0; i < a.size(); i++) {
    System.out.print(a[i]);
}
System.out.println();

INTERMEDIATE

Two additional statement types, break and continue, can also control the behavior of for loops.

ADVANCED

The break and continue statements can be used with statement labels.

for loops

`for` loops