Java do while loop
In this chapter you will learn:
- Why do we need Java do while loop
- Syntax for Java do while loop
- Example - How to use do-while statement
- How to create a simple help menu with while loop and switch statement
Description
To execute the body of a while loop at least once, you can use the do-while loop.
Syntax
Its general form is:
do {
// body of loop
} while (condition);
Example
Here is an example to show how to use a do-while loop.
public class Main {
public static void main(String args[]) {
int n = 10;// w ww . j av a 2s.co m
do {
System.out.println("n:" + n);
n--;
} while (n > 0);
}
}
The output:
The loop in the preceding program can be written as follows:
public class Main {
public static void main(String args[]) {
int n = 10;/*w w w .j a v a2 s .com*/
do {
System.out.println("n:" + n);
} while (--n > 0);
}
}
The output is identical the result above:
Example 2
The following program implements a very simple help system with do-while
loop and switch statement.
public class Main {
public static void main(String args[]) throws java.io.IOException {
char choice;/*from w ww .j a va 2s. co m*/
do {
System.out.println("Help on:");
System.out.println(" 1. A");
System.out.println(" 2. B");
System.out.println(" 3. C");
System.out.println(" 4. D");
System.out.println(" 5. E");
System.out.println("Choose one:");
choice = (char) System.in.read();
} while (choice < '1' || choice > '5');
System.out.println("\n");
switch (choice) {
case '1':
System.out.println("A");
break;
case '2':
System.out.println("B");
break;
case '3':
System.out.println("C");
break;
case '4':
System.out.println("D");
break;
case '5':
System.out.println("E");
break;
}
}
}
Here is a sample run produced by this program:
Next chapter...
What you will learn in the next chapter:
- When to use break statement
- Syntax for break statement
- Example - How to exit a for loop for a condition
- Example - break ut of a while loop
- How to use break statement to exit an infinite loop
- How to break just one layer of the nested loop
- How to break from a switch statement
- How to break where you want