Some simple debugging tools related to Java. These are for those who are new to Java.
1.
Application is crashing : Most miserable one. Get your log file, try to
analysis log. How to write log file, use Java Logger API. Java Logger
had been introduced in JDK 1.4.2. The most awesome feature of Logger
API is that you can use it in production without much overhead. The
overhead is controlled by something called level in API. Level goes
from FINEST to SEVERE. You can refer to O'Relly Book "Java, In a NutShell". I guess. ...........
Back to Java :). Here is a small blog on how to manage Java Process from Java itself.
Long back, I had written one blog on how to list Java Process
running on System by Java Code. But with the new features of JDK6, you
can not only see the list but can manage the other running Java
Process. This is possible using class LocalVirtualMachine. This class
has a list of methods :
Here I am just showing a simple code, which will again tell you all the running Java Process.
import sun.tools.jconsole.*;
import java.util.*;
public class Main {
public static void main(String[] args) {
Map map = LocalVirtualMachine.getAllVirtualMachines();
Iterator iter = map.values().iterator();
LocalVirtualMachine vm = null;
while (iter.hasNext()) {
vm = (LocalVirtualMachine)iter.next();
System.out.println(vm.displayName());
}
}
}
A very very small code :). Note that this class is not in rt.jar so we
need to add jconsole.jar and tools.jar in the classpath section.
So, for running we need to use :
D:/Program Files/Java/jdk1.6.0_11/bin/ControlJavaApp>../javac -cp "D:/Program Fi
les/Java/jdk1.6.0_11/lib/jconsole.jar" Main.java
D:/Program Files/Java/jdk1.6.0_11/bin/ControlJavaApp>../java -cp .;"D:/Program F
iles/Java/jdk1.6.0_11/libjconsole.jar";"D:Program Files/Java/jdk1.6.0_11/lib/t
ools.jar" Main
Or we can modify classpath in Env. Variables.
Right now, in my system it is displaying:
Main
org/netbeans/modules/javafx/preview/Main 1
That means, this code itself and Netbeans is running as a java process.
In next blog, we will try to see how to manage(not listing) other running java code from a java code. I am not able to find too much of doc from net, so things are slow :).
With Plug-in 2(Java 6u10), a whole new experience comes into Java Plug-in. I have mentioned the new features of Plugin2 in some of my presentations of 6u10.
Now, see the market increase in Java Gaming.And there is a reason behind it, people start realizing that Java is fast and a suitable language for gaming. It happened for quite a long time developed used to think that Java is a slow language and not meant for game.
Defense: This is quite an interesting market. It speaks about the robustness and security of Java. Defense finds it the best language for their purpose.
One guy asked a question on a Java Forum: which operation is faster - post-increment or pre-increment. I really don't feel these things make a big difference in code performance. I have written a small code to check what nanosecond API of Java is telling about it. And again I reached to a wrong benchmarking.
class InstructionCheck {
private int x = 0;
public void countup_() {
++x;
}
public void countup() {
x++;
}
public void countdown() {
x--;
}
public void count2up() {
x = x+2;
}
public void count2down() {
x = x-2;
}
public static void main(String[] args) {
long stime = 0;
long etime = 0;
InstructionCheck ic = new InstructionCheck();
stime = System.nanoTime();
ic.countup_();
System.out.println(System.nanoTime() - stime);
stime = System.nanoTime();
ic.countup();
System.out.println(System.nanoTime() - stime);
stime = System.nanoTime();
ic.countdown();
System.out.println(System.nanoTime() - stime);
stime = System.nanoTime();
ic.count2up();
System.out.println(System.nanoTime() - stime);
stime = System.nanoTime();
ic.count2down();
System.out.println(System.nanoTime() - stime);
}
}
And the output after several run:
20952 5308 5587 5587 5308
Now, no doubt the first value is not correct, because of some other reason(I really don't know why) but may be some reigster setting, first time using the class or something else.
But if we see the assemble code, it will simple say that there is(should) no difference in ++i or i++. Look at this :
The complete assemble code, you can see by option javap -c FileName. My personal opinion is to check the instruction set rather checking the time by nanosecond or millisecond because some benchmarking issue can lead to a different result(which can be completely wrong, like in our case). Here we can easily see that ++i and i++ leads to same instruction and hence both will be more or less equal in performace.
Few days back, I got a problem in which actually I have to get the fields, constructor and method name from a java class. One can think of using reflection API and the problem is easy to solve, but that is not the case. Reflection API can only be used on class files not Java file. Than a quick idea came into mind to compile the file internally, use reflection and then delete the class file, if user don't want to see it. This is never be a tough job if I use JDK6 JavaCompiler code which is :
import java.io.IOException;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class JDK6FirstCompile {
public static void main(String args[]) throws IOException {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
int results = compiler.run(null, null, null, "HelloWorld.java");
System.out.println("Success: " + (results == 0));
}
}
class HelloWorld {
public static void main(String args[]) {
System.out.println("Hello, World");
}
}
But but, I was constraint to use JDK5 or less. So, this JDK6 API is not worth for me :-(. Finally, came up with a small code, which probably can do this in all the case. Hoping it will not lose any generic behavior and run in all cases.
Here is the code:
import java.io.*;
public class CompileCheck {
public void compileClasses2() {
try {
String command = System.getProperty("java.home")+File.separator + ".." + File.separator+"bin"+File.separator+"javac " + "HelloWorld.java";
System.out.println(command);
Runtime.getRuntime().exec(command);
} catch (Exception e) { }
}
public static void main(String[] args) {
CompileCheck c = new CompileCheck();
c.compileClasses2();
}
}
In place of HelloWorld, I can surely use any path where the java file resides. And off course, I can use *.java as well :-). Please let me know your opinion or any other method easier than this from which I can get class methods, attributes and all from a java file.
Last week, IEC celebrates OpenSource Mela. In code war, we got a programming contest in which the problem statement is :
5 * 4 / 2 - 5 + 2 = 7 (evaluated from left to right). So, input format is:
5 4 2 5 2 7
and output is to put into a valid expression format(all possible format). So, if its 2 2 4, then 2+2=4 and 2*2=4 is possible. I have written some code for this, which goes here :
package problemstatement1;
import java.util.List;
public class Main {
String input = "2 0 2";
String output = new String(); // 5 * 4 / 2 - 5 + 2 = 7
int resultVal = 0;
String operatorseq = new String();
int result = 0;
int totalcounter = 0;
boolean flag = true;
// converting input into easy format
String[] inputtoken = input.split(" ");
int[] numberseq = new int[inputtoken.length - 1];
int totaloperator = numberseq.length - 1;
public void isValid() {
if (inputtoken.length < 3) {
System.out.println("Usages ... Input Parameter should be three or more ");
System.exit(0);
}
}
public void processInput() {
try {
resultVal = Integer.parseInt(inputtoken[inputtoken.length - 1]);
} catch(NumberFormatException e) {
System.out.println("Parsing error" + " " + e);
System.exit(0);
}
for (int i = 0; i < numberseq.length; i++) {
try {
numberseq[i] = Integer.parseInt(inputtoken[i]);
} catch(NumberFormatException e) {
System.out.println("Parsing error" + " " + e);
System.exit(0);
}
}
}
public void showInput() {
for (int i = 0; i < numberseq.length; i++) {
// System.out.println(numberseq[i]);
}
}
public void getPermutation() {
GenerateOperators gen = new GenerateOperators("+-*/", totaloperator);
List<String> v = gen.getVariations();
System.out.println("Possible Solutions");
for (int i = 0; i < v.size(); i++) {
operatorseq = v.get(i);
manupulate();
}
}
public void manupulate() {
result = 0;
for (int i = 0; i < operatorseq.length(); i++) {
if (i == 0) {
if ((operatorseq.charAt(i)) == '+') {
result = result + (numberseq[i] + numberseq[i + 1]);
}
if ((operatorseq.charAt(i)) == '-') {
result = result + (numberseq[i] - numberseq[i + 1]);
}
if ((operatorseq.charAt(i)) == '*') {
result = result + (numberseq[i] * numberseq[i + 1]);
}
if ((operatorseq.charAt(i)) == '/') {
try {
result = result + (numberseq[i] / numberseq[i + 1]);
} catch(Exception e) {
flag = false;
// don't do anything
}
}
} else {
if ((operatorseq.charAt(i)) == '+') {
result = result + numberseq[i + 1];
}
if ((operatorseq.charAt(i)) == '-') {
result = result - numberseq[i + 1];
}
if ((operatorseq.charAt(i)) == '*') {
result = result * numberseq[i + 1];
}
if ((operatorseq.charAt(i)) == '/') {
try {
result = result / numberseq[i + 1];
} catch(Exception e) {
flag = false;
// don't do anything
}
}
}
}
if (result == resultVal && flag == true) {
totalcounter++;
System.out.println("");
for (int i = 0; i < numberseq.length - 1; i++) {
System.out.print(numberseq[i] + "" + operatorseq.charAt(i));
}
System.out.print(numberseq[numberseq.length - 1]);
System.out.print("= " + result);
}
}
public void count() {
if(totalcounter == 0 ) {
System.out.println("NO EXPRESSION POSSIBLE");
System.exit(0);
}
else {
System.out.println("");
System.out.println("Total Possible Solution :" + totalcounter);
}
}
public static void main(String[] args) {
Main main = new Main();
main.isValid();
main.processInput();
main.showInput();
main.getPermutation();
main.count();
}
}
and one more file which is :
package problemstatement1;
import java.util.List;
import java.util.ArrayList;
public class GenerateOperators {
private String a;
private int n;
public GenerateOperators(String a, int n) {
this.a = a;
this.n = n;
}
public List<String> getVariations() {
int l = a.length();
int permutations = (int) Math.pow(l, n);
char[][] storeCombination = new char[permutations][n];
for (int x = 0; x < n; x++) {
int temp = (int) Math.pow(l, x);
for (int p1 = 0; p1 < permutations;) {
for (int al = 0; al < l; al++) {
for (int p2 = 0; p2 < temp; p2++) {
storeCombination[p1][x] = a.charAt(al);
p1++;
}
}
}
}
List<String> result = new ArrayList<String>();
for (char[] permutation : storeCombination) {
result.add(new String(permutation));
}
return result;
}
public static void main(String[] args) {
GenerateOperators gen = new GenerateOperators("AAAMMBR", 7);
List<String> v = gen.getVariations();
for (int i=0;i<v.size();i++) {
String s1 = v.get(i);
System.out.println(s1);
}
}
}
I did some fine tuning in my blog page after long time :-). I have added two more link in Links section, which can be helpful in :
1. Telling which JRE's are there on your machine(blog readers) machine.
2. And second will install the latest JRE(It will start installation directly, so careful :-D)
Alright, So now again one post for JavaFX. Finally I am able to write tracing path code in JavaFX. I have seen this in lot of Physics Motions where they show motion with tracing effect. Have a look at the output :
Here the ball is moving in a cosine fashion and so the trace. Easiest way to achieve this is to write code in update method. Have a look on the code, its small:
Some lines in code are filling those fancy colors in ball(some lines are hard coded as well).I am a real bad guy in filling nice catchy colors(this color looks like a sun and a moon combination). Any comments/improvements are welcome !
This is one simulation of Golden Eyes :-D(with an ugly face). I tried to make one use of Gaussian Blur which is applied in the white color of eyes. Adding this spot in the eyes gives a real simulation.
We are welcoming all the Java Engineers in Bangalore to join BOJUG. Its Bangalore Open Java Users Group. Before going into the schedule of this time meet, we motivate you to join the BOJUG group at: http://bojug.wikispaces.com/ and http://bojug.dev.java.net. Now, here are the talks of the week:
The next Bangalore Open Java Users Group (BOJUG) (http://bojug.dev.java.net)
meet has been planned for Saturday August 30, 2008,Time: 11.30 AM .
Venue:
Thoughtworks Bangalore
Tower C, Corporate Block, Diamond District, Airport Road
Landmarks: The first set of buildings after the Indiranagar flyover,
opp to the TJIF restaurant.
1. Java FX..Its just the beginning-Vaibhav Choudhary
JavaFX Preview SDK
NetBeans Compatibilty
Demo, Demo, Demo, Demo .. and only Demo. How to make timeline, reflection, constraint,easing, shapes, animation, Java AWT/Swing.
Last we will try to see how to use it in applet or any type of web code.
2. Beans Binding and Beans Validation- Sathish
Kumar
Short discussion on the above topics
3. Tomcat Internals - Sriram Narayanan
In this talk, Sriram will cover in brief various Tomcat configuration issues (server.xml, how to avoid having to deploy during development
time, etc). He'll next cover interesting topics such as developing custom Tomcat components, and how the component assembly mechanism
works.
It looks good, so I decided to put before the completion of work. I was trying to simulate some fancy effects on button, so that I can embed it somewhere in some site. Here what is the class for Button:
public class Button extends CustomNode {
public attribute x: Number;
public attribute y: Number;
public attribute text: Text;
public attribute rectangle: Rectangle;
public attribute content: String;
public function create(): Node {
Now, the buttons will look like:
If you move the focus on any of the button, it will shine like this :
or like this :
This simple 2 line animation is achieved by playing with the opacity code. Though I am not able to fit my text inside the button which currently I am trying to bind out. But simple flashy buttons are easy to achieve. Here is the code:
package flashybutton;
import javafx.scene.CustomNode;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.text.*;
import javafx.scene.geometry.*;
import javafx.scene.paint.Color;
import javafx.application.Frame;
import javafx.application.Stage;
import javafx.ext.swing.TextField;
import javafx.scene.Font;
import javafx.scene.FontStyle;
import javafx.scene.paint.*;
import javafx.input.MouseEvent;
var x: Number = 100;
var y: Number = 100;
var color: Color;
var buttons:Button[];
var text: Text;
var content: String;
var width: Number = 100;
var height: Number = 40;
var arcWidth:Number = 10;
var arcHeight: Number = 10;
var opacity: Number = 0.6;
for( i in [1..5] ) {
insert Button {
x:100 + 100 * i,
y:100,
content: "HelloWorld" + i,
opacity: 0.6
} into buttons;
}
Frame {
title: "MyApplication"
width: 1000
height: 200
closeAction: function() { java.lang.System.exit( 0 );
}
visible: true
stage: Stage {
fill: Color.BLACK
content: [
buttons
]
}
}
public class Button extends CustomNode {
public attribute x: Number;
public attribute y: Number;
public attribute text: Text;
public attribute rectangle: Rectangle;
public attribute content: String;
public function create(): Node {
return Group {
content: [
Rectangle {
x : bind x,
y : bind y,
fill: LinearGradient {
startX: 0.0
startY: 0.0
endX: 1.0
endY: 0.0
proportional: true
stops: [
// Stop { offset: 0.0 color: Color.BLACK },
Stop { offset: 0.0 color: Color.BLACK },
Stop { offset: 0.5 color: Color.GOLD },
Stop { offset: 1.0 color: Color.BLACK }
]
},
width: 100
height: 40
arcWidth: 10
arcHeight: 10
opacity: bind opacity
onMouseMoved: function( e: MouseEvent ):Void {
opacity = 1.0;
}
onMouseExited: function( e: MouseEvent ):Void {
opacity = 0.6;
}
},
Text {
x: bind x + 10,
y: bind y + height / 2 + arcHeight / 2;
content: bind content
}
]
}
}
}
As written in the last blog, now we can use those MotionBall into giving some kind of motion. Here I have tried to give a simple motion of ball under gravity. After every hit there is an energy dissipation and the ball will slow down at end. The colors of balls, initial positions and radius are all random but under a constraint.
Now, the motion of the balls should get called in timeline. Like this:
var timeline = Timeline {
repeatCount: Timeline.INDEFINITE
keyFrames : [
KeyFrame {
time : 16ms
action: function():Void {
for(ball in balls) {
ball.motion();
}
}
}
]
}
Here is the final code. I tried to write the value as generic as possible but pardon me if there is some hardcoded value written somewhere :
import javafx.scene.CustomNode;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.geometry.*;
import javafx.animation.Timeline;
import javafx.animation.KeyFrame;
import javafx.scene.paint.*;
import javafx.application.Frame;
import javafx.application.Stage;
import javafx.scene.effect.*;
// Java Legacy
import java.lang.Math;
import java.util.Random;
import java.lang.System;
var balls:GravityBall[];
var gravity:Number= 0.1;
var width:Number = 1200;
var height:Number= 500;
var dampFactor: Number = 0.9;
var timeline = Timeline {
repeatCount: Timeline.INDEFINITE
keyFrames : [
KeyFrame {
time : 16ms
action: function():Void {
for(ball in balls) {
ball.motion();
}
}
}
]
}
var rnd : Random = new Random();
for( i in [1..5] ) {
insert GravityBall {
x : rnd.nextInt( 100 ), y : rnd.nextInt( 300 ), radius : rnd.nextInt( 10 ) + 20
color : Color.rgb(rnd.nextInt(255),rnd.nextInt(255),rnd.nextInt(255))
, opacity : 0.9
} into balls;
}
var rect = Rectangle {
x: 0, y: 500
width: 1200, height: 10
fill: LinearGradient {
startX: 0.0
startY: 0.0
endX: 1.0
endY: 0.0
proportional: true
stops: [
Stop { offset: 0.0 color: Color.TRANSPARENT },
Stop { offset: 1.0 color: Color.WHITESMOKE }
]
}
}
Frame
{
title: "MyApplication"
width: 1200
height: 732
closeAction: function() { java.lang.System.exit( 0 );
}
visible: true
stage: Stage {
fill : Color.BLACK
content: [
balls,
rect
]
}
}
timeline.start();
public class GravityBall extends CustomNode {
public attribute x : Number;
public attribute y : Number;
public attribute radius : Number;
public attribute color : Color;
public attribute velocity : Number;
public function motion(): Void {
velocity += gravity;
x += 1;
y += velocity;
if(x + radius > width ) {
x = width - radius; //for ending at the boundary
}
if( y + radius > height ) {
y = height - radius;
velocity *= -dampFactor;
}
}
public function create(): Node {
return Circle {
centerX : bind x, centerY : bind y, radius : bind radius
fill: bind color
};
}
}
Hi, I am Vaibhav. I am working in Java and JavaFX group. This blog is about writing simple code and application in Java and newly launched JavaFX. I am working in Bangalore, India.
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