testsimple.java

JAVA 2入门经典 练习答案

// Chapter 7 Exercise 1

public class TestSimple {
  // This is just an exercise in catching exceptions.
  // The test of whether your code is OK is: does it throw the exceptions?

  public static void main(String args[]) {
    int result = 0;                   // Somewhere to store a result.
    int arraySize = 3;		
    int badSize = -1;                 // A negative size to generate NegativeArraySizeException.
    int[] array = null;                // Define an integer array variable.

    for(int choice = 0; choice<3 ; choice++)
    try {
      switch(choice) {
        case 0:		
         result = array[0];         // Generates a NullPointerException.
         break;
        case 1:		
         array = new int[badSize];  // Generates a NegativeArraySizeException.
         break;
        case 2:		
         array = new int[arraySize];    
         result = array[arraySize]; // Generates an ArrayIndexOutOfBoundsException.
         break;
      }
    }
    
    catch(NullPointerException e) {           // Catch the NullPointerException:
      System.out.println("\nNullPointerException Exception caught. " +
                         "Message in NullPointerException is:\n" +
                         "\n" + e + "\n");
      System.out.println("The contents of the stack trace are:\n");
      e.printStackTrace();
    }
    
    catch(NegativeArraySizeException e) {     // Catch the NegativeArraySizeException:
      System.out.println("\nNegativeArraySizeException Exception caught. " + 
                         "Message in NegativeArraySizeException is:\n" +
                         "\n" + e + "\n");
      System.out.println("The contents of the stack trace are:\n");
      e.printStackTrace();
    }
    
    catch(ArrayIndexOutOfBoundsException e) { // Catch the ArrayIndexOutOfBoundsException:
      System.out.println("\nArrayIndexOutOfBoundsException Exception caught. " +
                         "Message in ArrayIndexOutOfBoundsException is:\n" +
                         "\n" + e + "\n");
      System.out.println("The contents of the stack trace are:\n");
      e.printStackTrace();
    }
  }
}