Programming Tutorials

Using break to Exit a Loop

By: Baski Printer Friendly Format    

By using break, you can force immediate termination of a loop, bypassing the conditional expression and any remaining code in the body of the loop. When a break statement is encountered inside a loop, the loop is terminated and program control resumes at the next statement following the loop. Here is a simple example:

// Using break to exit a loop.
class BreakLoop {
public static void main(String args[]) {
for(int i=0; i<100; i++) {
if(i == 10) break; // terminate loop if i is 10
System.out.println("i: " + i);
}
System.out.println("Loop complete.");
}
}

This program generates the following output:

i: 0
i: 1
i: 2
i: 3
i: 4
i: 5
i: 6
i: 7
i: 8
i: 9
Loop complete.

As you can see, although the for loop is designed to run from 0 to 99, the break statement causes it to terminate early, when i equals 10. The break statement can be used with any of Java's loops, including intentionally infinite loops. For example, here is the preceding program coded by use of a while loop. The output from this program is the same as just shown.

// Using break to exit a while loop.
class BreakLoop2 {
public static void main(String args[]) {
int i = 0;
while(i < 100) {
if(i == 10) break; // terminate loop if i is 10
System.out.println("i: " + i);
i++;
}
System.out.println("Loop complete.");
}
}

When used inside a set of nested loops, the break statement will only break out of the innermost loop. For example:

// Using break with nested loops.
class BreakLoop3 {
public static void main(String args[]) {
for(int i=0; i<3; i++) {
System.out.print("Pass " + i + ": ");
for(int j=0; j<100; j++) {
if(j == 10) break; // terminate loop if j is 10
System.out.print(j + " ");
}
System.out.println();
}
System.out.println("Loops complete.");
}
}

This program generates the following output:

Pass 0: 0 1 2 3 4 5 6 7 8 9
Pass 1: 0 1 2 3 4 5 6 7 8 9
Pass 2: 0 1 2 3 4 5 6 7 8 9
Loops complete.

As you can see, the break statement in the inner loop only causes termination of that loop. The outer loop is unaffected. Here are two other points to remember about break. First, more than one break

statement may appear in a loop. However, be careful. Too many break statements have the tendency to destructure your code. Second, the break that terminates a switch statement affects only that switch statement and not any enclosing loops.

Note: break was not designed to provide the normal means by which a loop terminated. The loop's conditional expression serves this purpose. The break statement should be used to cancel a loop only when some sort of special situation occurs.