import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class KConstant {
    public final static char[] keys = new char[]
	{'0','1','2','3','4','5','6','7','8','9','+','='};
    public final static long INTERVAL = 100;
}
public class Keyboard extends InputStream {
    final private JPanel panel= new JPanel();
    public Keyboard(){
	super();
	for(char c : KConstant.keys){
	    JButton button = new JButton(String.valueOf(c));
	    button.addActionListener(new ButtonAction());
	    panel.add(button);
	}
    }
    public JPanel getPanel(){
	return panel;
    }
    public ActionListener getCloseAction(){
	return new CloseAction();
    }
    class CloseAction implements ActionListener {
	public CloseAction(){}
	public void actionPerformed(ActionEvent event){
	    queue.addLast(-1);
	}
    }
    class ButtonAction implements ActionListener {
	public ButtonAction(){}
	public void actionPerformed(ActionEvent event){
	    queue.addLast((int)(event.getActionCommand().charAt(0)));
	}
    }
    private LinkedList<Integer> queue= new LinkedList<Integer>();
    @Override
    public int read() throws IOException {
	try {
	    while(queue.isEmpty()){
		Thread.sleep(KConstant.INTERVAL);
            }
	}catch(InterruptedException e){
	}
	return queue.remove();
    }
    @Override
    public int available() throws IOException {
	return 0;
    }
    @Override
    public int read(byte[] b, int off, int len) throws IOException {
	if(len==0){
	    return 0;
	}
	int c = read();
	if(c==-1){
	    return -1;
	}
	b[off]=(byte) c;
	return 1;
    }
}