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What are Chained Exceptions?

One exception can be related to another using chained exceptions. We can use the chained exception mechanism in situations where we frequently need to throw a custom exception but want to retain the specifics of an original exception.

Constructors Of Throwable class Which support chained exceptions in java :

• Throwable(Throwable cause): Where cause is the exception that causes the current exception.
• Throwable(String msg, Throwable cause): where msg is the message for the current exception and cause is the exception that caused it.

Methods Of Throwable class Which support chained exceptions in java :

• getCause(): This method provides the precise cause of an exception.
• initCause(Throwable cause): method establishes the calling exception’s cause.

Example:

public class ExceptionHandling
{
 public static void main(String[] args)
 {
  try
  {
   // Creating an exception
   NumberFormatException ex =
     new NumberFormatException("Exception");

   // Setting a cause of the exception
   ex.initCause(new NullPointerException(
     "Coderzpy set the cause of the exception"));

   // Throwing an exception with cause.
   throw ex;
  }

  catch(NumberFormatException ex)
  {
   // displaying the exception
   System.out.println(ex);

   // Getting the actual cause of the exception
   System.out.println(ex.getCause());
  }
 }
}

Output:

java.lang.NumberFormatException: Exception
java.lang.NullPointerException: Coderzpy set the cause of the exception

Note: also read about the Interface vs Abstract class

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