separation.java

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//: Separation.java
// Separating GUI logic and business objects
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

class BusinessLogic {
	private int modifier;

	BusinessLogic(int mod) {
		modifier = mod;
	}
	
	public void setModifier(int mod) {
		modifier = mod;
	}

	public int getModifier() {
		return modifier;
	}
	
	// Some business operations:
	public int calculation1(int arg) {
		return arg * modifier;
	}

	public int calculation2(int arg) {
		return arg + modifier;
	}
}

public class Separation extends Applet {
	TextField
		t = new TextField(20),
		mod = new TextField(20);
	BusinessLogic bl = new BusinessLogic(2);
	Button
		calc1 = new Button("Calculation 1"),
		calc2 = new Button("Calculation 2");

	public void init() {
		add(t);
		calc1.addActionListener(new Calc1L());
		calc2.addActionListener(new Calc2L());
		add(calc1); add(calc2);
		mod.addTextListener(new ModL());
		add(new Label("Modifier:"));
		add(mod);
	}

	static int getValue(TextField tf) {
		try {
			return Integer.parseInt(tf.getText());
		} catch(NumberFormatException e) {
			return 0;
		}
	}
	
	class Calc1L implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			t.setText(Integer.toString(
				bl.calculation1(getValue(t))));
		}
	}

	class Calc2L implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			t.setText(Integer.toString(
				bl.calculation2(getValue(t))));
		}
	}

	class ModL implements TextListener {
		public void textValueChanged(TextEvent e) {
			bl.setModifier(getValue(mod));
		}
	}
	
	public static void main(String[] args) {
		Separation applet = new Separation();
		Frame aFrame = new Frame("Separation");
		aFrame.addWindowListener(
			new WindowAdapter() {
				public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
		aFrame.add(applet, BorderLayout.CENTER);
		aFrame.setSize(200,200);
		applet.init();
		applet.start();
		aFrame.setVisible(true);
	}
} ///:~