Learn CHEERPJ with Real Code Examples

# cheerpj/demo/Main.java
public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, CheerpJ!");
    }
}

A basic Java program compiled with CheerpJ that prints 'Hello, CheerpJ!' in the browser console.

# cheerpj/demo/ButtonClick.java
import javax.swing.*;
import java.awt.event.*;

public class ButtonClick {
    public static void main(String[] args) {
        JFrame frame = new JFrame("CheerpJ Button");
        JButton button = new JButton("Click Me");
        button.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
        System.out.println("Button clicked!");
        }
        });
        frame.add(button);
        frame.setSize(200,200);
        frame.setVisible(true);
    }
}

A Java program that creates a button and prints to console when clicked (via CheerpJ).

# cheerpj/demo/InputDialog.java
import javax.swing.*;

public class InputDialog {
    public static void main(String[] args) {
        String name = JOptionPane.showInputDialog("Enter your name:");
        System.out.println("Hello, " + name + "!");
    }
}

Shows an input dialog and prints user input to console.

# cheerpj/demo/Conditional.java
public class Conditional {
    public static void main(String[] args) {
        boolean isTrue = true;
        if (isTrue) {
        System.out.println("Condition is true");
        } else {
        System.out.println("Condition is false");
        }
    }
}

Prints different messages based on a condition.

# cheerpj/demo/Loop.java
public class Loop {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
        System.out.println("Item " + i);
        }
    }
}

Prints a list of items using a loop.

# cheerpj/demo/Timer.java
import java.util.Timer;
import java.util.TimerTask;
import java.util.Date;

public class TimerExample {
    public static void main(String[] args) {
        Timer timer = new Timer();
        timer.scheduleAtFixedRate(new TimerTask() {
        public void run() {
        System.out.println(new Date());
        }
        }, 0, 1000);
        while(true) {}
    }
}

Uses a timer to print current time every second.

# cheerpj/demo/LabelUpdate.java
import javax.swing.*;
import java.awt.event.*;

public class LabelUpdate {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Label Update");
        JLabel label = new JLabel("Initial Text");
        JButton button = new JButton("Update");
        button.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
        label.setText("Updated Text");
        }
        });
        frame.setLayout(new java.awt.FlowLayout());
        frame.add(label);
        frame.add(button);
        frame.setSize(300,100);
        frame.setVisible(true);
    }
}

Updates a JLabel when a button is clicked.

# cheerpj/demo/Dialog.java
import javax.swing.*;

public class Dialog {
    public static void main(String[] args) {
        JOptionPane.showMessageDialog(null, "Hello, CheerpJ Dialog!");
    }
}

Shows a message dialog using JOptionPane.

# cheerpj/demo/ArrayLoop.java
public class ArrayLoop {
    public static void main(String[] args) {
        String[] items = {"A", "B", "C"};
        for (String item : items) {
        System.out.println(item);
        }
    }
}

Iterates over an array and prints each element.

# cheerpj/demo/NestedLoops.java
public class NestedLoops {
    public static void main(String[] args) {
        for (int i = 1; i <= 3; i++) {
        for (int j = 1; j <= 3; j++) {
        System.out.print(i*j + " ");
        }
        System.out.println();
        }
    }
}

Uses nested loops to print a pattern.