Java do while loop
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 . ja v a 2 s . c om*/
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;// ww w . j av a 2 s .c o m
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 ava2 s. c o 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:
