How do I use the boolean negation (!) operator in Java?

By Wayan in Basic, Core API 0 Comment

The ! operator is a logical compliment operator. The operator inverts the value of a boolean expression.

package org.kodejava.basic;

public class NegationOperator {
    public static void main(String[] args) {
        // negate the result of boolean expressions
        boolean negate = !(2 < 3);
        boolean value = !false;

        System.out.println("result: " + negate);
        System.out.println("value : " + value);
    }
}

Here is the result of the program:

result: false
value : true

How do I use the || operator in Java?

By Wayan in Basic, Core API 0 Comment

The || operator or conditional OR operator operates on two boolean expressions. This operator exhibit “short-circuiting” behavior, which means that the second operand is evaluated only if needed.

The || operator evaluate only boolean values. For an OR (||) expression it will return true if either of the operand is true. If the first operand resolves true, then the second operand will not evaluate, because the complete expression will return true.

package org.kodejava.basic;

public class ConditionalORDemo {
    public static void main(String[] args) {
        // the second operand (5<3) is not evaluated, because the
        // first operand return true, the result of complete
        // expression will be true
        boolean a = (1 == 1) || (5 < 3);

        // the first operand return false, the second operand is
        // evaluated to check the result of the second expression.
        // If the second operand resolves to true, the complete
        // expression return true, otherwise return false.
        boolean b = (5 < 3) || (2 == 3);
        boolean c = (5 < 3) || (1 == 1);

        System.out.println("result a: " + a);
        System.out.println("result b: " + b);
        System.out.println("result c: " + c);
    }
}

The program prints the following output:

result a: true
result b: false
result c: true

How do I set the font and color of JTextArea?

By Wayan in Swing 0 Comment

To set the font and color of JTextArea we can use the setFont() and setForeground() methods of the JTextArea. To create a font we must define the font name, the font style and its size. For the colors we can uses the constant color values defined by the Color class.

package org.kodejava.swing;

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

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

    private static void showFrame() {
        JPanel panel = new TextAreaFontDemo();
        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(TextAreaFontDemo::showFrame);
    }

    private void initializeUI() {
        this.setLayout(new BorderLayout());
        this.setPreferredSize(new Dimension(500, 200));

        JTextArea textArea = new JTextArea(5, 40);
        textArea.setLineWrap(true);
        textArea.setText("The quick brown fox jumps over the lazy dog.");

        // Sets JTextArea font and color.
        Font font = new Font("Segoe Script", Font.BOLD, 20);
        textArea.setFont(font);
        textArea.setForeground(Color.BLUE);
        JScrollPane scrollPane = new JScrollPane(textArea);

        this.add(scrollPane, BorderLayout.CENTER);
    }
}

Here is the program screenshot of the code snippet above:

JTextArea Font and Color Demo

How do I create an uneditable JTextArea?

By Wayan in Swing 1 Comment

The following example shows you how to set the property of the JTextArea so that it cannot be edited or modified. To make the JTextArea not editable call the setEditable() method and pass a false value as the parameter.

package org.kodejava.swing;

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

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

    public static void showFrame() {
        JPanel panel = new TextAreaNotEditable();
        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(TextAreaNotEditable::showFrame);
    }

    private void initializeUI() {
        this.setLayout(new BorderLayout());
        this.setPreferredSize(new Dimension(500, 200));

        JTextArea textArea = new JTextArea(5, 50);
        textArea.setText("The quick brown fox jumps over the lazy dog.");

        // By default, the JTextArea is editable, calling
        // setEditable(false) produce uneditable JTextArea.
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea);

        this.add(scrollPane, BorderLayout.CENTER);
    }
}

The output of the code snippet is:

Uneditable JTextArea Demo

How do I use the && operator in Java?

By Wayan in Basic, Core API 0 Comment

The && operator also known as conditional-AND operator or short circuit AND. This operator exhibit “short-circuiting” behavior, which means that the second operand is evaluated only if needed.

The && operator evaluate only boolean values. For an AND (&&) expression to be true, both operands must be true. If the first operand resolves false, then the && operator will not evaluate the second operand, because it already know the complete expression will return false.

package org.kodejava.basic;

public class ConditionalANDDemo {
    public static void main(String[] args) {
        // second operand (2<3) is not evaluated, because the first
        // operand return false the result of complete expression
        // can't be true
        boolean a = (5 < 3) && (2 < 3);

        // first operand return true, second operand is evaluated
        // to check the result of the second expression if second
        // operand resolves to true, the complete expression return
        // false, otherwise return false
        boolean b = (1 == 1) && (2 < 3);
        boolean c = (1 == 1) && (5 < 3);

        System.out.println("result a: " + a);
        System.out.println("result b: " + b);
        System.out.println("result c: " + c);
    }
}

The result of the code snippet:

result a: false
result b: true
result c: false