lecture3-流程控制思考题

[wenuanhappy]

以下代码的第３２行可以省略么？为什么？

1   
2    // Compare integers using if structures, relational operators 
3    // and equality operators.
4    
5    // Java extension packages
6    import javax.swing.JOptionPane;
7    
8    public class Comparison {
9    
10      // main method begins execution of Java application
11      public static void main( String args[] )
12      {
13         String firstNumber;   // first string entered by user
14         String secondNumber;  // second string entered by user
15         String result;        // a string containing the output
16         int number1;          // first number to compare
17         int number2;          // second number to compare
18   
19         // read first number from user as a string
20         firstNumber =
21            JOptionPane.showInputDialog( "Enter first integer:" );
22   
23         // read second number from user as a string
24         secondNumber =
25            JOptionPane.showInputDialog( "Enter second integer:" );
26         
27         // convert numbers from type String to type int
28         number1 = Integer.parseInt( firstNumber );
29         number2 = Integer.parseInt( secondNumber );
30   
31         // initialize result to empty String
32         result = "";
33   
34         if ( number1 == number2 )
35            result = number1 + " == " + number2;
36   
37         if ( number1 != number2 )
38            result = number1 + " != " + number2;
39   
40         if ( number1 < number2 )
41            result = result + "\n" + number1 + " < " + number2;
42   
43         if ( number1 > number2 )
44            result = result + "\n" + number1 + " > " + number2;
45   
46         if ( number1 <= number2 )
47            result = result + "\n" + number1 + " <= " + number2;
48   
49         if ( number1 >= number2 )
50            result = result + "\n" + number1 + " >= " + number2;
51   
52         // Display results
53         JOptionPane.showMessageDialog(
54            null, result, "Comparison Results",
55            JOptionPane.INFORMATION_MESSAGE );
56   
57         System.exit( 0 );  // terminate application
58   
59      }  // end method main
60   
61   }  // end class Comparison

[ssjjcao]

不可以，变量result需要初始化。

[Guitenbay]

result是局部变量，没有初始值，所以需要第32行，否则会报错（已亲自试验）