In Eclipse IDE, go to Windows -> Preferences. A new window opens.
In left pane, click Java -> Editor -> Content Assit -> Advanced.
Now, in right pane top box, you can select Proposals to be shown in Default Proposal of Content Assist.
Finally, Click Ok to save the configuration and you are done.
import java.util.Random; /* library file to generate random number */
public class ParallelRankSort {
int[] list = new int[10];
int finallist[] = new int[10];
final int n = 10;
public void initialize(){
Random r = new Random(10);
for(int i=0; i<n; i++){
list[n-1-i] =r.nextInt(50);
}
}
public void runThreads(){
Thread t[] = new Thread[n];
for(int i=0; i<n; i++){
FindRank f = new FindRank(list[i],list,finallist);
t[i] = new Thread(f);
t[i].start();
}
for(int i=0; i<n; i++){
try {
t[i].join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public void displayOutput(){
//initial data
System.out.println(”Initial data”);
for(int i=0; i<n; i++){
System.out.println(”list[" + i + "] = ” + list[i]);
}
System.out.println(”After sorting”);
System.out.println(”");
for(int i=0; i<n; i++){
System.out.println(”finalList[" + i + "] = ” + finallist[i]);
}
}
public static void main(String[] args){
ParallelRankSort p = new ParallelRankSort();
p.initialize();
p.runThreads();
p.displayOutput();
}
}
//Runnable classes to be run by threads created above
class FindRank implements Runnable{
int data;
int list[];
int finallist[];
FindRank(int data, int[] list, int finallist[]){
this.data = data;
this.list = list;
this.finallist = finallist;
}
public void run(){
int count =0 ;
for(int i=0; i<list.length; i++){
if(list[i]<data){
count++;
}
}
finallist[count] = data;
}
}
The output obtained is shown below.
Initial data
list[0] = 14
list[1] = 31
list[2] = 38
list[3] = 47
list[4] = 6
list[5] = 46
list[6] = 40
list[7] = 43
list[8] = 30
list[9] = 13
After sorting
finalList[0] = 6
finalList[1] = 13
finalList[2] = 14
finalList[3] = 30
finalList[4] = 31
finalList[5] = 38
finalList[6] = 40
finalList[7] = 43
finalList[8] = 46
finalList[9] = 47
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In my earlier post, I have shown demo of External Complete Reverse Iterator for Iterator Pattern.In this post, I am going to show demo of External and Internal Selective Iterator done in Java. Selective Iterator iterates through the collection but leaves the elements which do not meet criteria specified in predicate logic.
For this to implement using Iterator pattern, major requirements are : functor interface, concrete functor class, predicate interface, concrete predicate class, customized collection (like Vector, Arraylist), Object class, selective Iterator and main application.
Functor interface and class are used to implement certain function. The function is included in an object which executes the function based on input parameters. The functor call is like below.
Functor<Swimmer> functor = new SwimmerFunctor(JTextArea2);
functor.process(swimmer);
And its implementation is like below.
public void process(Swimmer swimmer){
textArea.append(swimmer.getFname()+” “+swimmer.getLname()+ ” \n”);
}
Using this technique to delegate work to another object is called functor pattern.
Predicate is also a special functor but it always return true or false. In my example, I have used predicate to check whether the age of swimmer is above or equal to 12 or not.
A selective Iterator uses predicate to check whether to iterate through a particular element or not.
The iteration loop becomes like this
Functor<Swimmer> functor = new SwimmerFunctor(JTextArea2);
Predicate<Swimmer> pred = new SwimmerPredicate();
Iterator<Swimmer> swIterator = slist.selectiveIterator(pred);
while(swIterator.hasNext()){
Swimmer swimmer = swIterator.next();
functor.process(swimmer);
}
If iteration is placed inside the collection, then it becomes Internal selective Iteration. If placed outside, it becomes External Selective Iteratoration.
In the demo, I have created Swimmer as object and added 9 swimmers of age 11 and 12 to customized concrete collection of type myList. An external complete built-in iterator is used to populate all the swimmers in first JTextArea of JFrame. The selective external iterator is used to populate swimmers that have age of 12 or greater in the second JTextArea of the JFrame. Also, I have created a method inside myList named doAll(Functor<T> functor, Predicate<T> pred) which does selective iteration inside the myList i.e. Internal Selective Iteration.
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First of all, I created a customized collection myList which extends built-in Vector. It has got two methods.
1. revIterator(): It returns IteratorReverse that I am going to create
2. doAll(): It processes all the elements of collection internally using functor.
doAll() implementation is simple. It is shown below.
//method to to internal reverse operation (phase 3)
public void doAll(Functor<T> functor){
Iterator<T> it = this.revIterator();
while(it.hasNext()){
functor.process(it.next());
}
}
But here, IteratorRevese (implementing Iterator and returned by revIterator) has to return element from reverse side of collection. The implementation of IteratorReverse goes like below.
public class IteratorReverse<T> implements Iterator<T>{
myList<T> myList;
int index; //to maintain state or to maintain position of it in collection
I have implemented next() and hasNext() method as follows.
@Override
public T next() {
if(index>= myList.size()){
return null;
}
else{
T t = myList.elementAt(myList.size()-index-1);
index = index +1;
return t;
}
}
@Override
public boolean hasNext() {
if(index>= myList.size()){
return false;
}
else
return true;
}
IteratorReverse use generics for type safety and reuse. The following summarizes the main logic of back reversal
T t = myList.elementAt(myList.size()-index-1);
When we forward ‘index’ keeps on increasing while myList.size()-index-1 keeps on decreasing.
I have implemented Functor pattern through interface. SwimmerFunctor is concrete implementation of Interface Functor which takes JTextArea2 from mainApp as argument and appends text into it as shown in picture above.
As shown in figure above, when ‘All Swimmers’ button is pressed, it will use built-in Iterator and iterates through the collection in forward direction. But when ‘All Swimmers Backward’ button is pressed, it will use IteratorReverse and iterates through the collection in backward direction.
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First of all, we have to create a JFrame window which acts as container for all components. Then we have to add JMenuBar in it. The JMenuBar will contain JMenus and each JMenu will contain JMenuItems. During actual coding we go in reverse order. First we create JMenuItems. We give a label to it and add ActionListener to it. ActionListener is the way of saying JVM (Java Virtual Machine) which method to execute when the user clicks the particular JMenuItem. After that, we create JMenus and add those created JMenuItems in required JMenus. Then after, we create JMenuBar and add those JMenus in it in required order. Finally, we attach the JMenuBar to the JFrame. To demonstrate all these, I have created two java files - AppMenuBar.java and JMenuTest.java. The Full source code with descriptive comments can be downloaded here. – Source Code.
Sample code
To create JMenuItem.
JMenuItem item = new JMenuItem(“Show All Empty Seats”);
item.addActionListener(this);
This creates a menu item with label ‘Show All Empty Seats’ and adds itself (the object which is calling the statement—the object of class AppMenuBar).
JMenu showMenu = new JMenu(“Show”);
showMenu.add(item);
These above statements create a JMenu with label ‘Show’ and add a JMenuItem created above.
The signature of actionPerformed() method in class which implements the ActionListener Interface should be like this.
public void actionPerformed(ActionEvent e) {
if(e.getActionCommand()==“Reserve a Seat”){
jMenuTest.showMessage(“A Seat Reserved”);
}
}
Finally, the JMenus created above can be added to JMenuBar like below.
JMenuBar menubar = new JMenuBar();
menubar.add(showMenu);
The menubar created above can be set as JMenuBar of the JFrame as below.
setJMenuBar(menubar);
In the source code attached, AppMenuBar.java creates a JMenuBar with a JMenu named ‘Show’ with 2 JMenuItems and another JMenu named ‘Transaction’ with 4 JMenuItems. AppMenuBar class inherits built-In class JMenuBar. It also implements ActionListener Interface class. That’s why, it has got actionPerformed() method. Any class which implemensts ActionListener Interface can be action listener of the JMenuItem and those classes will have actionPerformed() method. I have used this actionPerformed() method to change the Message label text of the calling JFrame.
JMenuTest class inherits the built-in classs JFrame. In constructor method, it creates an AppMenuBar and sets that as its JMenuBar. Also, it creates a JLabel and adds that to it. I have not use any layout format so far, so the JLabel is added to middle covering the entire JFrame container. I will discuss more on the Layouts in forth coming posts. The final output picture is shown below.
JMenu Test Sample Picture
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There are two levels of access control.
1. At the Class level – ‘public’ or nothing(package-driven or default)
a. If a class is defined as public, it can be accessed from all the classes anywhere (means from any package).
b. If a class is defined without any modifier, then it is package-driven that means, it is only visible inside the package in which it is defined.
2. At the Data Member level – ‘public’, ‘protected’, ‘private’ or nothing(package-driven or default)
a. If a data member of a class is defined as public as shown below, then it can be seen from anywhere.
i. public int a;
b. If a data member of a class is defined as protected, then it can be accessed only in its class and its child classes.
c. If a data member of a class is defined as private, then it can be only accessed in its class.
d. If a data member is defined without any modifier, then it is package-driven. So, it is visible inside the package where it is defined.
The above rules defined for data member also applies for the methods of a class.
The following table summarizes the rules discussed above.
Access Levels
Modifier Class Package Subclass World
Public Y Y Y Y
protected Y Y Y N
no modifier Y Y N N
private Y N N N
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