Cara sortir di Java

Tanpa perlu basa-basi saya akan memberikan sedikit tutorial yakni bagaimana cara menyortir list di java. Seperti kita ketahui list itu sendiri merupakan suatu kumpulan objek. Untuk keperluan sortir sendiri, java sudah menyediakan fasilitas built-in ke kita. Yakni dengan menggunakan utilitas pada java Collections. Berdasarkan informasi yang saya peroleh, algoritma yang digunakan dalam java sorting ini adalah merge sort [1]. Tanpa perlu berbasa basi saudara tinggal menyalin contoh berikut dan langsung di running di komputer anda.

	package test;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Comparator;
	import java.util.Random;
	public class Sortir {
	Random rand = new Random();
	public Sortir() {
	String a = "";
	int m = 100;
	for(int i=0; i< 12; i++){
	int aa = rand.nextInt(m);
	int bb ;
	if( aa % 2 != 0){
	bb = m-1 - aa;
	}else{
	bb = m-1 - aa -1;
	aa = aa + 1;
	}
	for(int j=0; j < bb/2; j++)
	a = a+ " ";
	for(int j=0; j< aa; j++)
	a = a + "*";
	for(int j=0; j < bb/2; j++)
	a = a+ " ";
	list.add(a);
	a = "";
	}
	Collections.sort(list, new Comparator<String>() {
	public int compare(String p1, String p2){
	return p1.lastIndexOf("*") > p2.lastIndexOf("*")? 1
	: p1.lastIndexOf("*") < p2.lastIndexOf("*")?-1:0;
	}
	});
	for(int i=0; i< list.size();i++){
	System.out.println(list.get(i));
	}
	}
	ArrayList<String> list = new ArrayList<>();
	public static void main(String[] args){
	new Sortir();
	}
	}

view raw Sortir.java hosted with ❤ by GitHub

Jika sudah maka hasil yang akan ditampilkan adalah sebagai berikut:

	*********
	*******************
	*****************************
	*****************************************
	***********************************************
	*********************************************************
	***********************************************************
	***********************************************************
	***************************************************************
	*****************************************************************
	*************************************************************************
	*******************************************************************************************

view raw hasil.txt hosted with ❤ by GitHub

1. http://www.coderanch.com/t/520171/java/java/Collections-sort-merge-sort-insteadof

Animasi Bola Biliard dengan JavaFX

Kali ini saya akan memberikan sebuah tutorial mengenai bagaimana membuat animasi bola billiard dengan javaFX yang preview-nya dapat dilihat pada gambar berikut:

 

Adapun source codenya adalah sebagai berikut:

package fjr.collision;

import java.util.ArrayList;
import java.util.Random;

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBuilder;
import javafx.scene.shape.Circle;
import javafx.scene.shape.CircleBuilder;
import javafx.stage.Stage;
import javafx.util.Duration;

public class BilliardBallDetection extends Application {

  ArrayList listParticle;
 ArrayList listCircle; 

 double xwidth = 400;
 double ywidth = 400;

 double timeStep = 2.5;
 double numberParticle = 9;
 Random rand = new Random();

 double dmin = 30.0;

 double xmax = xwidth;
 double xmin = 0.0;
 double ymax = ywidth;
 double ymin = 0.0;
 double size = 0.0;

 double dmax = 0.0;
 
 double vmax = 3.0; 


 Timeline animation; 
 Button buttonPause, buttonPlay; 
 
 @Override
 public void start(Stage primarySrage) throws Exception {
  // TODO Auto-generated method stub
  generateParticle();
  removeOverlap(listParticle);
  generateCircle();
  
  Group root = new Group(); 
  for(int i =0; i< listCircle.size(); i++){
   Circle c = listCircle.get(i); 
   root.getChildren().add(c); 
  }
  
  animation = new Timeline(); 
  animation.setCycleCount(Timeline.INDEFINITE);
  animation.setAutoReverse(false);
  
  KeyFrame kf = new KeyFrame(Duration.millis(20), new EventHandler(){

   @Override
   public void handle(ActionEvent event) {
    // TODO Auto-generated method stub
    checkBoundary();
    calculateCollision();
    moveParticle(); 
    redrawCircle();
   }
   
  }); 

  animation.getKeyFrames().add(kf); 
  
  root.getChildren().addAll(buttonPlay = ButtonBuilder.create()
    .text("PLAY").onAction(new EventHandler() {

     @Override
     public void handle(ActionEvent arg0) {
      // TODO Auto-generated method stub
      animation.play();
     }
    }).translateX(10).translateY(10)
    .build(), 
    buttonPause = ButtonBuilder.create()
    
    .text("PAUSE").translateX(80).translateY(10)
    .onAction(new EventHandler() {

     @Override
     public void handle(ActionEvent arg0) {
      // TODO Auto-generated method stub
      animation.pause();
     }
    })
    .build() 

    ); 
  primarySrage.setScene(new Scene(root, xwidth, ywidth));
  primarySrage.show();
 }
 
 private void redrawCircle(){
  for(int i=0; i< listCircle.size(); i++){
   Circle c = listCircle.get(i); 
   Particle  p  = listParticle.get(i); 
   c.setCenterX(p.x);
   c.setCenterY(p.y);
  }
 }
 
 
 private void generateCircle(){
  listCircle = new ArrayList<>(); 
  for(int i=0; i< listParticle.size(); i++){
   Particle p = listParticle.get(i); 
   Circle c = CircleBuilder.create()
     .centerX(p.x).centerY(p.y).radius(dmin)
     .build(); 
   listCircle.add(c);
  }
 }

 private void generateParticle() {
  listParticle = new ArrayList<>();
  for (int i = 0; i < numberParticle; i++) {
   Particle particle = new Particle(rand.nextDouble() * xwidth,
     rand.nextDouble() * ywidth, rand.nextDouble() * vmax,
     rand.nextDouble() * vmax);
   listParticle.add(particle);
  }
 }


 private void calculateCollision(){
  for(int i=0; i< listParticle.size(); i++){
   Particle p1  = listParticle.get(i); 
   for(int j= i+1; j< listParticle.size(); j++ ){
    Particle p2 = listParticle.get(j); 
    chekCollision(p1, p2);
   }
  }
 }
 
 public void chekCollision(Particle p1, Particle p2) {
  
  if (isOverlap(p1, p2)) {
   
   double deltaX = p1.x - p2.x;
   double deltaY = p1.y - p2.y;
   double distance =  Math.sqrt(deltaX * deltaX + deltaY * deltaY);
   deltaX = deltaX/ distance;
   deltaY = deltaY/distance; 
   
   double aci = p1.vx * deltaX + p1.vy * deltaY; 
   double bci = p2.vx * deltaX + p2.vy * deltaY; 
   
   double acf = bci; 
   double bcf = aci; 
   
   p1.vx = p1.vx + (acf - aci) * deltaX; 
   p1.vy = p1.vy + (acf - aci) * deltaY; 
   p2.vx = p2.vx + (bcf - bci) * deltaX; 
   p2.vy = p2.vy + (bcf - bci) * deltaY;
  }
 }

 private void moveParticle() {
  for (int i = 0; i < listParticle.size(); i++) {
   Particle p = listParticle.get(i);
   p.x += p.vx * timeStep;
   p.y += p.vy * timeStep;
  }
 }


 public void removeOverlap(ArrayList list) {
  for (int i = 0; i < list.size(); i++) {
   Particle p1 = list.get(i);
   for (int j = list.size() - 1; j > i; j--) {
    Particle p2 = list.get(j);
    if(isOverlap(p1, p2))
     list.remove(j); 
   }
  }
 }
 
 public void checkBoundary(){
  for(int i =0; i< listParticle.size() ;i++){
   Particle p = listParticle.get(i); 
   if(p.x > xmax - dmin)
    p.vx = -Math.abs(p.vx) ;
   if(p.x < xmin + dmin)
    p.vx = Math.abs(p.vx); 
   if(p.y > ymax - dmin)
    p.vy = - Math.abs(p.vy);
   if(p.y < ymin + dmin)
    p.vy = Math.abs(p.vy); 
  }
 }
 
 private boolean isOverlap(Particle p1, Particle p2){
  double deltax = p1.x - p2.x; 
  double deltay = p1.y - p2.y; 
  if(deltax * deltax + deltay * deltay < 4 * dmin * dmin)
   return true; 
  return false; 
 }
 
 public static void main(String[] args) {
  launch(args);
 }

 private class Particle {
  double x = 0.0;
  double y = 0.0;
  double vx = 0.0;
  double vy = 0.0;
  public Particle(double x, double y , double vx , double vy ) {
   this.x = x;
   this.y = y;
   this.vx  = vx ;
   this.vy = vy; 
  }
 }
}

Deteksi tumbukan dengan javaFX

Pada tutorial ini saya akan memberikan  bagaimana cara mendeteksti tumbukan dengan javaFX yang previewnya dapat dilihat pada gambar berikut:

Adapaun source codenya adalah:

package fjr.collision;

import java.util.Random;

import javafx.application.Application;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBuilder;
import javafx.scene.shape.Circle;
import javafx.scene.shape.CircleBuilder;
import javafx.stage.Stage;

public class TestCollision extends Application {

 double r = 14.0;
 Random rand = new Random();

 double xwidth = 400;
 double ywidth = 400;

 int numberParticle = 100;

 // uji tumbukan
 public boolean testCol(Circle p1, Circle p2) {
  double dx = p1.getCenterX() - p2.getCenterX();
  double dy = p1.getCenterY() - p2.getCenterY();
  if (dx * dx + dy * dy < 4 * r * r) {
   return true;
  }
  return false;
 }

 public void removeOverlap(ObservableList list) {
  for (int i = 0 ; i< list.size() ; i++ ) {
   if (list.get(i) instanceof Circle) {
    Circle p1 = (Circle) list.get(i);
    for (int j = list.size()- 1 ; j   > i ; j-- ) {
     if (list.get(j) instanceof Circle) {
      Circle p2 = (Circle) list.get(j);
      if (testCol(p1, p2)) {
       list.remove(j);
      }
     }
    }
   }
  }
 }

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

 Button button, button1;
 boolean state = true;

 @Override
 public void start(Stage primaryStage) throws Exception {

  final Group root = new Group();
  primaryStage.setScene(new Scene(root, xwidth, ywidth));

  for (int i = 0; i < numberParticle; i++) {
   root.getChildren().add(
     CircleBuilder.create().centerX(rand.nextDouble() * xwidth)
       .centerY(rand.nextDouble() * ywidth).radius(r)
       .build());
  }

  button = ButtonBuilder.create().text("ORGANIZE").translateX(10)
    .translateY(10).build();
  button1 = ButtonBuilder.create().text("RESET").translateX(100)
    .translateY(10).build();

  root.getChildren().addAll(button, button1);

  button.setOnAction(new EventHandler() {

   @Override
   public void handle(ActionEvent arg0) {
    if (state) {
     removeOverlap(root.getChildren());
    }
    state = false;
   }
  });

  button1.setOnAction(new EventHandler() {

   @Override
   public void handle(ActionEvent arg0) {
    for (int i = root.getChildren().size() - 1; i >= 0; i--) {
     root.getChildren().remove(i);
    }

    for (int i = 0; i < numberParticle; i++) {
     root.getChildren().add(
       CircleBuilder.create()
         .centerX(rand.nextDouble() * xwidth)
         .centerY(rand.nextDouble() * ywidth)
         .radius(r).build());
    }
    root.getChildren().addAll(button, button1);
    state = true;
   }
  });

  primaryStage.show();

 }
}

Export gambar ke kode Latex

Seperti kita ketahui bahwa  menggambar di  Latex itu biasanya menggunakan  beberapa library, di mana dua di antaranya yang paling populer adalah tikZ dan pstrick. Dalam menggunakan kedua librari ini otomatis kita harus menuliskan kode-kodenya. Masalahnya adalah kode-kode ini tidak mudah dihapal, sehingga sangat menyulitkan bagi kita yang tidak punya banyak waktu untuk keperluan ini. 

Oleh karena itu beberapa developer  sudah  menyediakan fasilitas untuk mengeksport gambar yang dibuat tool-tool gui yang ada ke kode Latex. Beberapa  software yang punya kapasitas ini antara lain, adalah:

1. Dia http://dia-installer.de/ : mempunyai banyak fasilitas dan built-in library untuk menggambar diagram atau sirkuit elektronik. Dan hasilnya bisa dieksport ke kode Latex:

2. Inkscape, http://inkscape.org/ : 

Akan tetapi untuk inkscape ini, yang versi 0.48 hanya tersedia untuk pstrick. Masalahnya adalah pstrick sendiri kurang portable jika dibandingkan  dengan tikZ. 

3. MatplotLib (http://matplotlib.org/users/whats_new.html#pgf-tikz-backend). Yang terakhir ini merupakan library dari python untuk keperluan plot.