Exceptions handling
Exceptions
Throwable class

Common constructors of the Throwable class

Constructor	Description
Throwable()	Creates a new exception with a null message.
Throwable(message)	Creates a new exception with the specified message.

Common methods of the Throwable class

Method	Description
getMessage()	Returns the message associated with the exception, if one is available.
printStackTrace()	Prints the stack trace to the standard error output stream along with the value of the toString method of the exception object.
printStackTrace(PrintWriter stream)	Prints the stack trace showing the sequence of method calls when an exception occurs. Output is sent to the stream specified by the parameter stream.
toString()	Returns a string that includes the name of the class that the exception was created from, along with the message associated with the exception, if one is available.

Code that throws an exception with a message

try
{
    throw new IOException("An IO error has occurred.");
}
catch (IOException e)
{
    System.err.println(e.getMessage());
    System.err.println(e.toString());
}

Resulting output

An IO error has occurred.
java.io.IOException: An IO error has occurred.

Code that uses the printStackTrace method

try
{
    throw new IOException("An IO error has occurred.");
}
catch (IOException e)
{
    e.printStackTrace(); }
}

Resulting output

java.io.IOException: An IO error has occurred.
   at ProductTestApp.getProductData(ProductTestApp.java:14)
   at ProductTestApp.main(ProductTestApp.java:7)

Code that uses the printStackTrace method

import java.io.*;
public class PrintStackTraceExample1
{
    public static void main(String[] args)
    {
        try
        {
            methodA();
        }
        catch (Exception e)
        {
            System.out.println(e.toString()  + " caught in main");
            e.printStackTrace();
        }
    }
    public static void methodA() throws Exception
    {
        methodB();
    }
    public static void methodB() throws Exception
    {
        methodC();
    }
    public static void methodC() throws Exception
    {
        throw new Exception("Exception generated " + "in method C");
    }
}

Resulting output

java.lang.Exception: Exception generated in method C caught in main
java.lang.Exception: Exception generated in method C
        at PrintStackTraceExample1.methodC
       (PrintStackTraceExample1.java:30)
        at PrintStackTraceExample1.methodB
        (PrintStackTraceExample1.java:25)
        at PrintStackTraceExample1.methodA
        (PrintStackTraceExample1.java:20)
        at PrintStackTraceExample1.main
        (PrintStackTraceExample1.java:9)