How to Re-Throw Exception in Java

In Java, throw is the most commonly used keyword to throw either a built-in exception or a -user-defined exception, but sometimes we have to throw the same exception through the catch block.

This situation is called the re-throwing an exception. In this tutorial article, we will learn about the re-throwing exception and perform this task without making any changes to the original stack trace.

Demonstration of Re-Throwing an Exception in Java

If you are working with sensitive programs, such as manipulating the database, tracking the exception is essential before propagating it to a higher level.

We need to perform some activities on the catch block and re-throw the exception so that the higher level of the program gets notified that an exception occurs in the system.

In our example below, we will re-throw an exception when a string value sets to null. The code for this purpose will be like the below:

public class JavaException {
  public static void main(String args[]) {
    String Name = null;

    try {
      if (Name.equals("Mark"))
        System.out.println("Matched"); // This will cause NullPointerException
    } catch (Exception e) {
      throw e;
    }
  }
}

In the above code fence, we first set the value of a string variable Name to null. After that, we used the exception handler of java try{ ... } catch { ... }, and inside it, we compared the string value with another string.

Now this will cause a NullPointerException error. After running the above example code, you will get the below output in your console.

Exception in thread "main" java.lang.NullPointerException
    at javacodes.JavaException.main(JavaException.java:8)

If we look at the code of the example sincerely, we will see that our code re-throws any exception is caught, and we get the original stack trace without making any changes.