How do I get the exponent of exponential function?

By I Wayan Saryada in Core API, Math 0 Comment

The exponential function is f(x) = ex. The Math.getExponent() method is used to get the x value of the given parameter, in which the parameter is a result of exponential function calculation.

package org.kodejava.math;

public class GetExponent {
    public static void main(String[] args) {
        double fx = 1.0d;
        float fx1 = 1.0f;

        int x = Math.getExponent(fx);
        System.out.println("Exponent  = " + x);

        // argument in float
        int xf = Math.getExponent(fx1);
        System.out.println("Exponent1 = " + xf);
    }
}

How do I calculate exponential function?

By I Wayan Saryada in Core API, Math 1 Comment

In mathematics, the exponential function is the function ex, where e is the number (approximately 2.718281828) such that the function ex equals its own derivative. The function f(x) = ex at the point x = 0 is equal to 1.

package org.kodejava.math;

public class ExponentExample {

    public static void main(String[] args) {
        double x = 0.0d;

        // calculates e raised to the power of x (e^x)
        double fx = Math.exp(x);

        // calculates e raised to the power of x minus 1 (e^x - 1)
        double fxm1 = Math.expm1(x);

        System.out.println("fx   = " + fx);
        System.out.println("fxm1 = " + fxm1);
    }
}

How do I calculate the length of hypotenuse?

By I Wayan Saryada in Core API, Math 0 Comment

Hypot is a mathematical function defined to calculate the length of the hypotenuse of a right-angle triangle. It was designed to avoid errors arising due to limited-precision calculations performed on computers.

From: Wikipedia

The Math.hypot(double x, double y) return the sqrt(x2+ y2) without intermediate overflow or underflow. The result will be same with this calculation Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2)).

package org.kodejava.math;

public class HypotExample {
    public static void main(String[] args) {
        double number1 = 3.0d;
        double number2 = 5.0d;

        // calculate square root of total value of
        // number1 ^ 2 + number2 ^ 2
        double sqr = Math.hypot(number1, number2);

        System.out.println("Total value = " +
                (Math.pow(number1, 2) + Math.pow(number2, 2)));
        System.out.println("Square root = " + sqr);
    }
}

How do I define a constant variable?

By I Wayan Saryada in Basic, Core API 0 Comment

To define a constant in Java, use final modifier which combined with static modifier. The final modifier indicates that the value of this field cannot change.

If you change the value of the constant, you need to recompile the class to get the current value. Other feature in Java that provide similar functionality is enumeration (a list of named constants). You can simply create an enumeration by using the enum keyword.

package org.kodejava.example.fundamental;

public class ConstantDemo {
    public static void main(String[] args) {
        int sunday = DayConstant.SUNDAY;
        System.out.println("Sunday = " + sunday);

        String dozen = MeasureConstant.DOZEN;
        System.out.println("Dozen  = " + dozen);
    }
}

class DayConstant {
    public final static int SUNDAY = 0;
    public final static int MONDAY = 1;
    public final static int TUESDAY = 2;
    public final static int WEDNESDAY = 3;
    public final static int THURSDAY = 4;
    public final static int FRIDAY = 5;
    public final static int SATURDAY = 6;
}

class MeasureConstant {
    final static String UNIT = "unit";
    final static String DOZEN = "dozen";
}

How do I remove tabs from JTabbedPane?

By I Wayan Saryada in Swing 1 Comment

To remove tabs from JTabbedPane we can use the following remove methods:

  • remove(int index) method to remove a tab at the specified index.
  • remove(Component component) method to remove a tab that has the specified child component.
  • removeAll() method to remove all tabs.
package org.kodejava.swing;

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

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

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

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

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

    private void initializeUI() {
        final JTabbedPane pane = new JTabbedPane(JTabbedPane.LEFT);
        pane.addTab("A Tab", new JPanel());
        pane.addTab("B Tab", new JPanel());

        JPanel tabPanel = new JPanel();
        pane.addTab("C Tab", tabPanel);
        pane.addTab("D Tab", new JPanel());
        pane.addTab("E Tab", new JPanel());

        // Remove the last tab from JTabbedPane
        pane.remove(pane.getTabCount() - 1);

        // Remove tab that contains a tabPanel component which is
        // the C Tab.
        pane.remove(tabPanel);

        JButton button = new JButton("Remove All Tabs");
        button.addActionListener(e -> {
            // Remove all tabs from JTabbedPane
            pane.removeAll();
        });

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

The output of the code snippet above is:

Remove Tabs from JTabbedPane