Java: 'for' Statement

Purpose

The purpose of the for statement is to repeat Java statements many times. It is similar to the while statement, but it is often easier to use if you are counting or indexing because it combines three elements of many loops: initialization, testing, and incrementing.

General Form

The for statement has this form:

for (init-stmt; condition; next-stmt) {
    do this each time
}

There are three parts in the for statement.

The init-stmt statement is done before the loop is started, usually to initial a variable.
The condition expression is tested at the beginning of each time the loop is done. The loop is stopped when this boolean expression is false (the same as the while loop).
The next-stmt statement is done at the end of every time through the loop, and usually increments a variable.

Example

Here is a loop written as both a while loop and a for loop. First using while:

count = 0;
while (count < 50) {
    g.drawLine(20, count*5, 80, count*5);
    count = count + 1;
}
g.drawString("Loop is finished.  count="+count, 10, 300);

And here is the same loop using for:

for (count=0; count < 50; count = count+1) {
    g.drawLine(20, count*5, 80, count*5);
}
g.drawString("Loop is finished.  count="+count, 10, 300);

Notice that the for loop is much shorter. It is better when you are counting something. Later you will see examples where the while loop may be the better choice.