How to use Java 1. 7 Multiple Catch Block with example - JDK 7 tutorial

As release of JDK 7 approaching General Availability (GA) on 2011/07/28, I thought to have a look on language enhancement as part of project coin, also called as Small language enhancements or JSR 334. Though there is not any major changes like Enum or Generics of Java 1.5,  but they are still very useful, in terms of simplifying your day to day programming task. Some of the interesting changes are allowing String in Switch cases,  , inclusion of fork join framework in JDK itself , , type inference using diamond operator, automatic resource management using  try with resource feature, and ability to catch multiple Exception in single catch block . In this Java 7 tutorial, we will learn how multi catch block of JDK 1.7 makes Exception handling code simpler and elegant. Multiple catch block will allow you to catch multiple exceptions in one block but it’s only available in JDK7 and you need to compiler your code with source 1.7. This article also shows you how to use JDK 7 multiple catch block with example. I also recommend book Java 7 Recipes: A Problem-Solution Approach to learn more about all the changes made in JDK 1.7 and how to make effective use of them.

JDK 1. 7 feature: Improved exception handling using multi-catch block

Java has always been criticized for having checked exception and polluting code with cluttered exception handling code, multi-catch block in Java 1.7  certainly assuage those wounds. With multi catch block,  you can catch multiple exceptions in one catch block, which will eventually result in more readable code. Prior to JDK 7 if you want to catch two exceptions, you need to provide two catch blocks and if you have same code to run on these two blocks, then either you need to use finally block or just duplicate the code on two catch blocks. finally block is  not an ideal solution, because it will execute even if Exception is not thrown so ultimately lot of duplicate code which sometime makes code unreadable and clumsy. Now with JDK7 multi catch block we can catch multiple exception in one catch block separated by pipe (|) and reduce the code duplication. Let’s see an example of multiple exceptions catching in Java 7.

public static void main(String args[]) {

    Scanner scnr = new Scanner(System.in);

    String number = scnr.next();

    try {

        if (number.length() > 5) {

            throw new IllegalArgumentException();

        }

        Integer.parseInt(number);

    } catch (NumberFormatException | IllegalArgumentException e) {

        e.printStackTrace();

    }

}

In above code example or JDK7 multi-catch block we have used multiple catch block of JDK 1.7 and control will come on this block whenever code throws either NumberFormatException or IllegalArgumentException.

Java 7  multiple catch block example tutorial

We have seen code making use of this new Java 7 feature of catching more than one Exception in one catch block. In our example, we are catching NumberFormatException and IllegalArgumentException together and her we will verify that by entering input which will result in both type of Exception one by one. If we are able to catch both Exception than it's proven.

Testing of JDK 1.7 multi-cache block  

If we will enter any number with alphabets, than it will throw NumberFormatException as shown below :

Input: 23ff

java.lang.NumberFormatException: For input string: "23ff"

        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)

        at java.lang.Integer.parseInt(Integer.java:492)

        at java.lang.Integer.parseInt(Integer.java:527)

        at jdk7demo.JDK7Demo.main(JDK7Demo.java:25)

Now let's enter number with more than 5 digit this will result in IllegalArgumentException as per our code.

Input :123333

java.lang.IllegalArgumentException

        at jdk7demo.JDK7Demo.main(JDK7Demo.java:23)

      

I used Netbeans 7 to compile and run this project. Setting up JDK 7 in Netbeans is very easy just download JDK7 and then click on Tool-->Java Platform and then click "Add Platforms" it will open a file browser just point out JDK7 installation directory and it will import JDK 1.7  binaries , source and docs and set it up for your use. One more thing you need to remember is that setting source as 1.7 because this new language feature is only available in JDK7. In next series of this JDK7 feature article we will see how to use String in Switch statement.





Recommended Book for further Reading

Java 7 Recipes: A Problem-Solution Approach By Josh Juneau, Carl Dea, Freddy Guime, John O'Conner

Source:http://javarevisited.blogspot.com/2011/07/jdk7-multi-cache-block-example-tutorial.html