15.7: Break and Continue
- Page ID
- 18893
Sometimes neither a pretest nor a posttest loop will provide exactly what you need. In the previous example, the “test” needed to happen in the middle of the loop. As a result, we used a flag variable and a nested if
-else
statement.
A simpler way to solve this problem is to use a break
statement. When a program reaches a break
statement, it exits the current loop.
Scanner in = new Scanner(System.in); while (true) { System.out.print("Enter a number: "); if (in.hasNextDouble()) { break; } String word = in.next(); System.err.println(word + " is not a number"); } double x = in.nextDouble();
Using true
as a conditional in a while
loop is an idiom that means “loop forever”, or in this case “loop until you get to a break
statement.”
In addition to the break
statement, which exits the loop, Java provides a continue
statement that moves on to the next iteration. For example, the following code reads integers from the keyboard and computes a running total. The continue
statement causes the program to skip over any negative values.
Scanner in = new Scanner(System.in); int x = -1; int sum = 0; while (x != 0) { x = in.nextInt(); if (x <= 0) { continue; } System.out.println("Adding " + x); sum += x; }
Although break
and continue
statements give you more control of the loop execution, they can make code difficult to understand and debug. Use them sparingly.