How do I create key press event using Robot class?

By I Wayan Saryada in AWT, Core API 0 Comment

In this example we use the java.awt.Robot class to generate a key press event. We can call the keyPress(int keyCode) method to produce this event.

package org.kodejava.awt;

import java.awt.AWTException;
import java.awt.Robot;
import java.awt.event.KeyEvent;

public class CreatingKeyboardEvent {
    public static void main(String[] args) {
        try {
            Robot robot = new Robot();

            // Create a three seconds delay.
            robot.delay(3000);

            // Generating key press event for writing the QWERTY letters
            robot.keyPress(KeyEvent.VK_Q);
            robot.keyPress(KeyEvent.VK_W);
            robot.keyPress(KeyEvent.VK_E);
            robot.keyPress(KeyEvent.VK_R);
            robot.keyPress(KeyEvent.VK_T);
            robot.keyPress(KeyEvent.VK_Y);
        } catch (AWTException e) {
            e.printStackTrace();
        }
    }
}

How do I create a screen capture using Robot class?

By I Wayan Saryada in AWT, Core API 0 Comment

In this example you’ll see how to create a screen capture / screenshot and save it as an image file such a PNG image. Some classes are use in this program including the java.awt.Robot, java.awt.image.BufferedImage and javax.imageio.ImageIO.

package org.kodejava.awt;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.io.File;
import java.io.IOException;

public class ScreenCapture {
    public static void main(String[] args) {
        try {
            Robot robot = new Robot();

            // Capture screen from the top left in 200 by 200 pixel size.
            BufferedImage bufferedImage = robot.createScreenCapture(
                    new Rectangle(new Dimension(200, 200)));

            // The captured image will the written into a file called
            // screenshot.png
            File imageFile = new File("screenshot.png");
            ImageIO.write(bufferedImage, "png", imageFile);
        } catch (AWTException | IOException e) {
            e.printStackTrace();
        }
    }
}

How do I convert BigInteger into another radix number?

By I Wayan Saryada in Core API, Math 0 Comment

In this example you’ll see how we can convert a java.math.BigInteger number into another radix such as binary, octal and hexadecimal.

package org.kodejava.math;

import java.math.BigInteger;

public class BigIntegerConversion {
    public static void main(String[] args) {
        BigInteger number = new BigInteger("2021");
        System.out.println("Number      = " + number);
        System.out.println("Binary      = " + number.toString(2));
        System.out.println("Octal       = " + number.toString(8));
        System.out.println("Hexadecimal = " + number.toString(16));

        number = new BigInteger("FF", 16);
        System.out.println("Number      = " + number);
        System.out.println("Number      = " + number.toString(16));
    }
}

The result of our examples:

Number      = 2021
Binary      = 11111100101
Octal       = 3745
Hexadecimal = 7e5
Number      = 255
Number      = ff

How do I do math operation for BigDecimal?

By I Wayan Saryada in Core API, Math 1 Comment 
package org.kodejava.math;

import java.math.BigDecimal;
import java.math.RoundingMode;

public class BigDecimalOperation {
    public static void main(String[] args) {
        BigDecimal decimalA = new BigDecimal("98765432123456789");
        BigDecimal decimalB = new BigDecimal("10");

        decimalA = decimalA.add(decimalB);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.multiply(decimalB);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.subtract(decimalB);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.divide(decimalB, RoundingMode.DOWN);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.pow(2);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.negate();
        System.out.println("decimalA = " + decimalA);
    }
}

Our code snippet results are:

decimalA = 98765432123456799
decimalA = 987654321234567990
decimalA = 987654321234567980
decimalA = 98765432123456798
decimalA = 9754610582533151990855052972412804
decimalA = -9754610582533151990855052972412804

How do I do math operation for BigInteger?

By I Wayan Saryada in Core API, Math 0 Comment 
package org.kodejava.math;

import java.math.BigInteger;

public class BigIntegerOperation {
    public static void main(String[] args) {
        BigInteger numberA = new BigInteger("98765432123456789");
        BigInteger numberB = BigInteger.TEN;

        numberA = numberA.add(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.multiply(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.subtract(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.divide(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.mod(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.pow(2);
        System.out.println("numberA = " + numberA);

        numberA = numberA.negate();
        System.out.println("numberA = " + numberA);
    }
}

Our class result are:

numberA = 98765432123456799
numberA = 987654321234567990
numberA = 987654321234567980
numberA = 98765432123456798
numberA = 8
numberA = 64
numberA = -64