1   // Example 2.3 IfDemo.java                         
2   //                                                            
3   //                                                            
4   // Copyright 2003 Bill Campbell and Ethan Bolker                         
5                                                               
6   
7   // A class illustrating the if-statement. A typical run:
8   //
9   // %> java IfDemo 
10  // Enter an integer: 0
11  // If 0 is negative, say hello:
12  // isNegative is false
13  // The integer 0 is zero
14  // Finally: 0 is still nonnegative
15  // because it's zero
16  
17  public class IfDemo 
18  {
19      public static void main( String[] args ) 
20      {
21          Terminal terminal = new Terminal();  // for input and output
22  
23          // Prompt for and read a single integer.
24          int var = terminal.readInt( "Enter an integer: " );
25          
26          // simple if statement
27          terminal.println( "If " + var + " is negative, say hello:" );
28          if (var < 0) {
29              terminal.println( "hello" );
30          }
31  
32          // an if-else statement testing a boolean variable
33          boolean isNegative = ( var < 0 );
34          if (isNegative) {
35              terminal.println( "isNegative is true" );
36          }
37          else {
38              terminal.println( "isNegative is false" );
39          } 
40  
41          // if-else-if statement
42          terminal.print( "The integer " + var + " is ");
43          if (var > 0) {
44              terminal.println("positive");
45          }
46          else if (var < 0) {
47              terminal.println( "negative" );
48          }
49          else { // just one case left!
50              terminal.println( "zero" );
51          }
52  
53          // finally, nested if-(if)-else: note the indenting
54          terminal.print( "Finally: " + var + " is still ");
55          if (var >= 0) {
56              terminal.println("nonnegative");
57              if (var == 0 ) {
58                  terminal.println("because it's zero ");
59              }
60          }
61          else {
62              terminal.println( "negative" );
63          }
64      }
65  }
66