Performance Improvement in JDK6

Original Post: http://blogs.sun.com/vaibhav/entry/why_jdk6_again

Content:

Again a comparison and reason why JDK6. Weeks back one of our team member gave a presentation on JVM performance improvement in Mustang. I have just collected a useful point here and try to compare with older JDK version. Here is the code:

import java.util.*;
public class RuntimePerformanceGC {
public static void main(String[] args) {
RuntimePerformanceGC ob = new RuntimePerformanceGC();
Vector v = new Vector();
java.util.Date now = new java.util.Date();
long t1 = now.getTime();
ob.addItems(v);
java.util.Date now1 = new java.util.Date();
System.out.println(now1.getTime()-t1);
}
public void addItems(Vector v) {
for(int i =0;i<500000;i++)
v.add("Item" + i);
}
}

And the output in ms is:

JDK1.4.2: 984

JDK 6: 578

You can see a massive difference. 37 percent improvement in time. Why ? Here goes :

This is because of Runtime Performance Optimization. The new lock coarsening optimization technique implemented in hotspot eliminates the unlock and relock operations when a lock is released and then reacquired with no meaningful work done in between those operations. And this is what happening in our example. Since, Vector do thread safe operation, it takes the lock for add, release the lock and then takes it again.

So, I just tried to give one more reason why use JDK6 ;-). This is off course not the only reason for big improvement, I will try to cover some more in upcoming blogs :-)

Java 6u10 Features

Sorry for not writing for a long time. Actually I have start writing more on Sun Blog Site, so this blog space get affected . But today I got time to archive some of my blog work on this site.
Here is the latest :

Current work: Presentation in BOJUG meet. Download here. Don't forgot to give your comments :-). There are some demos which I try to cover in blog.

These slides basically talks about Java SE 6u10 features. Some of them are cool like

-> Next Generation Plugin where you can drap plugin outside the browser.

-> Kernel JRE. Download small JRE.

-> Nimbus Look And Feel

-> New Applet feature

Disk Space Check

Take care of disk space when you are writing a big program :). Use JDK 6 features:

import java.io.File;

public class DiskSpaceCheck {
public DiskSpaceCheck() {
File file = new File("E:");
System.out.println("E:");
System.out.println("Total:  " + file.getTotalSpace());
System.out.println("Free:   " + file.getFreeSpace());
System.out.println("Usable: " + file.getUsableSpace());

file = new File("E://movie");
System.out.println("E://movie");
System.out.println("Total:  " + file.getTotalSpace());
System.out.println("Free:   " + file.getFreeSpace());
System.out.println("Usable: " + file.getUsableSpace());

file = new File("/");
System.out.println("n/");
System.out.println("Total:  " + file.getTotalSpace());
System.out.println("Free:   " + file.getFreeSpace());
System.out.println("Usable: " + file.getUsableSpace());
}

public static void main(String[] args) {
new DiskSpaceCheck();
}
}

I was actually very suprised that why this feature came so late.