Programming Reflection: How to use jdk7 multi-cache block with example

Sunday 19 May 2013

How to use jdk7 multi-cache block with example

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 were not major changes but they are very useful in terms of simplifying your day to day programming task. In this java tutorial we will see how multi-cache block in JDK7 makes Exception handling code simpler and elegant. Multi-cache 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 multi-cache block with example.

JDK7 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-cache block in JDK certainly assuage those wounds. With multi-cache block you can catch multiple exceptions in one block which will eventually result in less code and more readable code. Prior to JDK7 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 or just duplicate the code on two catch blocks. finally 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 JDK7

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-cache block we have used multi cache block of JDK7 and control will come on this block whenever code throws either NumberFormatException or IllegalArgumentException.

JDK7 multi-cache block example tutorial

Testing of JDK7 multi-cache block

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)

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 JDK7 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.