How do I append text to JTextArea?

By I Wayan Saryada in Swing 2 Comments

To append text to the end of the JTextArea document we can use the append(String str) method. This method does nothing if the document is null or the string is null or empty.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;

public class TextAreaAppendText extends JPanel {
    public TextAreaAppendText() {
        initializeUI();
    }

    public static void showFrame() {
        JPanel panel = new TextAreaAppendText();
        panel.setOpaque(true);

        JFrame frame = new JFrame("JTextArea Demo");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(TextAreaAppendText::showFrame);
    }

    private void initializeUI() {
        String text = "The quick brown fox ";

        JTextArea textArea = new JTextArea(text);
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        JScrollPane scrollPane = new JScrollPane(textArea);

        String appendText = "jumps over the lazy dog.";
        textArea.append(appendText);

        this.setPreferredSize(new Dimension(500, 200));
        this.setLayout(new BorderLayout());
        this.add(scrollPane, BorderLayout.CENTER);
    }
}

The output of the code snippet above is:

JTextArea Append Text Demo

How do I insert a text in a specified position in JTextArea?

By I Wayan Saryada in Swing 0 Comment

The insert(String str, int pos) of the JTextArea allows us to insert a text at the specified position. In the example below we insert brown and over words into the current JTextArea text.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;

public class TextAreaInsertText extends JPanel {
    public TextAreaInsertText() {
        initializeUI();
    }

    public static void showFrame() {
        JPanel panel = new TextAreaInsertText();
        panel.setOpaque(true);

        JFrame frame = new JFrame("JTextArea Demo");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(TextAreaInsertText::showFrame);
    }

    private void initializeUI() {
        String text = "The quick fox jumps the lazy dog.";

        JTextArea textArea = new JTextArea(text);
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        JScrollPane scrollPane = new JScrollPane(textArea);

        textArea.insert("brown ", 10);
        textArea.insert("over ", 26);

        this.setPreferredSize(new Dimension(500, 200));
        this.setLayout(new BorderLayout());
        this.add(scrollPane, BorderLayout.CENTER);
    }
}

The screenshot of the result from the code snippet above is:

JTextArea Insert Text Demo

How do I replace text in the JTextArea?

By I Wayan Saryada in Swing 0 Comment

In this example you’ll see how to use the replaceRange(String str, int start, int end) method to replace a string in the JTextArea from the start position to the end position with the specified string.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;

public class TextAreaReplaceText extends JPanel {
    public TextAreaReplaceText() {
        initializeUI();
    }

    public static void showFrame() {
        JPanel panel = new TextAreaReplaceText();
        panel.setOpaque(true);

        JFrame frame = new JFrame("JTextArea Demo");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(TextAreaReplaceText::showFrame);
    }

    private void initializeUI() {
        String text = "The quick white fox jumps over the sleepy dog.";

        JTextArea textArea = new JTextArea(text);
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        JScrollPane scrollPane = new JScrollPane(textArea);

        textArea.replaceRange("brown", 10, 15);
        textArea.replaceRange("lazy", 35, 41);

        this.setPreferredSize(new Dimension(500, 200));
        this.setLayout(new BorderLayout());
        this.add(scrollPane, BorderLayout.CENTER);
    }
}

The screenshot of the code snippet above is:

JTextArea Replace Text Demo

How do I use join method to wait for threads to finish?

By I Wayan Saryada in Core API, Lang Package 0 Comment

If you want a thread to work until another thread dies, you can join the thread onto the end of the another thread using the join() method. For example, you want thread B only work until thread A completes its work, then you want thread B to join thread A.

package org.kodejava.example.lang;

public class ThreadJoin implements Runnable {
    private int numberOfLoop;

    private ThreadJoin(int numberOfLoop) {
        this.numberOfLoop = numberOfLoop;
    }

    public void run() {
        System.out.println("[" +
            Thread.currentThread().getName() + "] - Running.");

        for (int i = 0; i < this.numberOfLoop; i++) {
            System.out.println("[" +
                Thread.currentThread().getName() + "] " + i);
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        System.out.println("[" +
            Thread.currentThread().getName() + "] - Done.");
    }

    public static void main(String[] args) {
        Thread t1 = new Thread(new ThreadJoin(10), "FirstThread");
        Thread t2 = new Thread(new ThreadJoin(20), "SecondThread");

        try {
            // start t1 and waits for this thread to die before
            // starting the t2 thread.
            t1.start();
            t1.join();

            // start t2
            t2.start();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

How do I set the priority of a thread?

By I Wayan Saryada in Core API, Lang Package 0 Comment

Threads always run with some priority, usually represented as a number between 1 and 10 (although in some cases the range is less than 10). A thread gets a default priority that is the priority of the thread of execution that creates it.

But, you can also set a thread’s priority directly by calling the setPriority() method on a Thread instance. One thing to remember about thread priorities is never rely on thread priorities, because thread-scheduling priority behavior is not guaranteed.

package org.kodejava.lang;

public class ThreadPriority extends Thread {
    private final String threadName;

    ThreadPriority(String threadName) {
        this.threadName = threadName;
    }

    public static void main(String[] args) {
        ThreadPriority thread1 = new ThreadPriority("First");
        ThreadPriority thread2 = new ThreadPriority("Second");
        ThreadPriority thread3 = new ThreadPriority("Third");
        ThreadPriority thread4 = new ThreadPriority("Fourth");
        ThreadPriority thread5 = new ThreadPriority("Fifth");

        // set thread1 to minimum priority = 1
        thread1.setPriority(Thread.MIN_PRIORITY);

        // set thread2 to priority 2
        thread2.setPriority(2);

        // set thread3 to normal priority = 5
        thread3.setPriority(Thread.NORM_PRIORITY);

        // set thread4 to priority 8
        thread4.setPriority(8);

        // set thread5 to maximum priority = 10
        thread5.setPriority(Thread.MAX_PRIORITY);

        thread1.start();
        thread2.start();
        thread3.start();
        thread4.start();
        thread5.start();
    }

    @Override
    public void run() {
        System.out.println("Running [" + threadName + "]");
        for (int i = 1; i <= 10; i++) {
            System.out.println("[" + threadName + "] => " + i);

            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}