Just fooling around with looking at Java exceptions today, I created the following sample code to see what the output from various exception-printing approaches looked like. I usually just follow the e.printStackTrace() approach, but I wanted to learn a little more about the options, as I was getting ready to print my exception information using a tool like Log4j.

So, here's the example Java source code for the exception testing class I created:

package com.devdaily.tests;

import java.io.File;
import java.io.FileInputStream;
import java.util.Arrays;
import java.util.Properties;

public class ExceptionTest
{

  public ExceptionTest()
  {
    Properties props = new Properties();
    try
    {
      props.load(new FileInputStream(new File("foo")));
    }
    catch (Exception e)
    {
      System.err.println("1");
      System.err.println(e);
      System.err.println("\n2");
      System.err.println(e.getMessage());
      System.err.println("\n3");
      System.err.println(e.getLocalizedMessage());
      System.err.println("\n4");
      System.err.println(e.getCause());
      System.err.println("\n5");
      System.err.println(Arrays.toString(e.getStackTrace()));
      System.err.println("\n6");
      e.printStackTrace();
    }
  }

  public static void main(String[] args)
  {
    new ExceptionTest();
  }
}

Given that simple test class, and knowing that there isn't a file named "foo", here's the output from the class:

1
java.io.FileNotFoundException: foo (The system cannot find the file specified)

2
foo (The system cannot find the file specified)

3
foo (The system cannot find the file specified)

4
null

5
[java.io.FileInputStream.open(Native Method), java.io.FileInputStream.(FileInputStream.java:106), com.devdaily.tests.ExceptionTest.(ExceptionTest.java:15), com.devdaily.tests.ExceptionTest.main(ExceptionTest.java:36)]

6
java.io.FileNotFoundException: foo (The system cannot find the file specified)
	at java.io.FileInputStream.open(Native Method)
	at java.io.FileInputStream.(FileInputStream.java:106)
	at com.devdaily.tests.ExceptionTest.(ExceptionTest.java:15)
	at com.devdaily.tests.ExceptionTest.main(ExceptionTest.java:36)

For my money, option #6 certainly prints out the information I'm looking for. The next thing to do is to try to integrated this with Log4j. I don't have Log4j on the system I'm typing this one, so I'll have to take a look at that tomorrow.