Name: tb29552 Date: 08/08/97


Sample Program


public class ExceptionDemo {
    public static void main(String argv[])
    {
        int i = 0;
        int j = 16;
        for ( j = 16; j >= 0; j-- )
        {
         i *= 2;
         try {
             i = 16/i;
         } catch(Exception e) {
             System.out.println("This doesn't Work!"); // line 12
         }
        }
    }
}



The Problem

If you set a break point at line 12 and stop at that location in the debugger,
you can't examine the Exception e.

Diagnosis

This is because the compiler doesn't generate a local variable table entry
for the exception object. Note that if the exception object is ever referenced
within the catch block, than the compiler does produce the variable table
entry - and the debugger can read it.

Here is a javap dump of the variable table information for this application:


D:\javabugs>javap -l ExceptionDemo
Compiled from ExceptionDemo.java
public synchronized class ExceptionDemo extends java.lang.Object
    /* ACC_SUPER bit set */
{
    public static void main(java.lang.String[]);
    public ExceptionDemo();
}

Line numbers for method void main(java.lang.String[])
   line 4: 0
   line 5: 2
   line 6: 5
   line 8: 11
   line 9: 15
   line 10: 15
   line 9: 20
   line 11: 23
   line 12: 24
   line 9: 32
   line 6: 35
   line 2: 42

Local variables for method void main(java.lang.String[])
   java.lang.String[] argv pc=0, length=43, slot=0
   int j pc=5, length=38, slot=2
   int i pc=2, length=41, slot=1

Line numbers for method ExceptionDemo()
   line 1: 0

Local variables for method ExceptionDemo()
   ExceptionDemo this pc=0, length=5, slot=0
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