suin.java

英文版本教材里面的习题几个小程序的代码

21Concurrency
Exercise 12:(3)Repair AtomicityTest.java using the synchronized keyword.Can you demonstrate that it is now correct?
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


public class AtomicityTest implements Runnable
{
	private int i = 0;
	public int getValue()
	{
		return i;
	}
	private synchronized void evenIncrement()
	{
		i++;
		i++;
	}
	public static void main(String[] args) 
	{
		ExecutorService exec = Executors.newCachedThreadPool();
		AtomicityTest at = new AtomicityTest();
		exec.execute(at);
		while(true)
		{
			int val = at.getValue();
			if(val % 2 != 0)
			{
				System.out.println(val);
				System.exit(0);
			}
		}
	}

	public void run() 
	{
		while(true)
			evenIncrement();
	}
}

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22Graphical User Interfaces
A selection of  Swing componets
Exercise 18:(4)Modify MessageBoxes.java so that it has an indidual ActionListener for each button (instead of matching the button text).
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import com.bruceeckel.swing.*;

class MessageBoxes extends JApplet {
  JButton
    b1 = new JButton("Alert"),
    b2 = new JButton("Yes/No"),
    b3 = new JButton("Color"),
    b4 = new JButton("Input"),
    b5 = new JButton("3 Vals");
  JTextField txt = new JTextField(15);
  public void init() {
    Container cp = getContentPane();
    cp.setLayout(new FlowLayout());
    cp.add(b1);
    cp.add(b2);
    cp.add(b3);
    cp.add(b4);
    cp.add(b5);
    cp.add(txt);
    b1.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        JOptionPane.showMessageDialog(null,
          "There's a bug on you!", "Hey!",
          JOptionPane.ERROR_MESSAGE);
      }
    });
    b2.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        JOptionPane.showConfirmDialog(null,
          "or no", "choose yes",
          JOptionPane.YES_NO_OPTION);
      }
    });
    b3.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        Object[] options = { "Red", "Green" };
        int sel = JOptionPane.showOptionDialog(
          null, "Choose a Color!", "Warning",
          JOptionPane.DEFAULT_OPTION,
          JOptionPane.WARNING_MESSAGE, null,
          options, options[0]);
          if(sel != JOptionPane.CLOSED_OPTION)
            txt.setText(
              "Color Selected: " + options[sel]);
      }
    });
    b4.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        String val = JOptionPane.showInputDialog(
            "How many fingers do you see?");
        txt.setText(val);
      }
    });
    b5.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        Object[] selections = {
          "First", "Second", "Third" };
        Object val = JOptionPane.showInputDialog(
          null, "Choose one", "Input",
          JOptionPane.INFORMATION_MESSAGE,
          null, selections, selections[0]);
        if(val != null)
          txt.setText(
            val.toString());
      }
    });
  }
}
 
public class E11_MessageAction {
  public static void main(String args[]) {
    Console.run(new MessageBoxes(), 200, 200);
  }
}
     
22Graphical User Interfaces
Exercise 1:(1)Modify HelloSwing.java to prove to yourself that the application will not close without the call to setDefaultCloseOperation().
//:gui/HelloSwing.java
import javax.Swing.*;
public class HelloSwing{
pubic static void main(String[] args){
JFrame frame = new JFrame("Hello Swing");
frame.setSize(300,100);
frame.setVisible(ture);
}
}