1   // Example 2.1 While1Demo.java
2   //
3   //
4   // Copyright 2003 Bill Campbell and Ethan Bolker
5   
6   // A class for illustrating the while-statement.  A typical run:
7   // 
8   // %> java While1Demo
9   // Enter integer (a negative to stop): 4
10  // 4 is non-negative.
11  // Enter integer (a negative to stop): -3
12  // 
13  // Enter integer (a negative to stop): 5
14  // 5 is non-negative.
15  // Enter integer (a negative to stop): -2
16  // Finally, enter integer you want to count to: 12
17  // Count 1 to 12: 1 2 3 4 5 6 7 8 9 10 11 12
18  
19  public class While1Demo
20  {
21      public static void main( String[] args ) 
22      {
23          Terminal terminal = new Terminal();  // for input and output
24          
25          // while tests a condition
26          int n = terminal.readInt("Enter integer (a negative to stop): ");
27          while ( n >= 0 ) {
28              terminal.println( n + " is non-negative." );
29              n = terminal.readInt("Enter integer (a negative to stop): ");
30          }
31          terminal.println();
32  
33          // while tests a boolean variable
34          boolean more = true;
35          while ( more ) {
36              n = terminal.readInt("Enter integer (a negative to stop): ");
37              if ( n >= 0 ) {
38                  terminal.println( n + " is non-negative." );
39              }
40              else {
41                  more = false;
42              }
43          }
44  
45          // while used for counting
46          n = terminal.
47              readInt("Finally, enter integer you want to count to: ");
48          int i = 1;
49          terminal.print( "Count 1 to " + n + ":" );
50          while ( i <= n ) {
51              terminal.print( " " + i );
52              i++;  //  same as i = i + 1
53          }
54          terminal.println();
55      }
56  }
57