import java.awt.*;
import javax.swing.*;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
import javax.swing.event.DocumentListener;
import java.text.NumberFormat;
import javax.swing.event.DocumentEvent;
import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
public class WangPeng extends JFrame
{
    private static final String[] calculate = {"+","-","*","/"};
    private JFormattedTextField text_1,text_2,text_3;
    private NumberFormat formatter = NumberFormat.getIntegerInstance();
    private JComboBox combox_char;

    public WangPeng()
    {
        super("整数的算术运算");

        this.setBackground(java.awt.Color.lightGray);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.getContentPane().setLayout(new FlowLayout());

        text_1 = new JFormattedTextField(formatter);
        text_1.setColumns(10);
        text_1.setValue(Long.valueOf(0));
        this.getContentPane().add(text_1);
        combox_char=new JComboBox(calculate);
        this.getContentPane().add(combox_char);

        text_2 = new JFormattedTextField (formatter);
        text_2.setValue(Long.valueOf(0));
        text_2.setColumns(10);
        this.getContentPane().add(text_2);
        this.getContentPane().add(new JLabel("="));
        text_3 = new JFormattedTextField (formatter);
        text_3.setColumns(10);
        text_3.setEditable(false);
        this.getContentPane().add(text_3);
        this.pack();
        this.setVisible(true);
        xxxxxxx();
    }

    private void xxxxxxx(){
        FocusListener listener = new FocusListener(){
                @Override
                public void focusGained(FocusEvent e){
                    compute();
                }
                @Override
                public void focusLost(FocusEvent e){
                    compute();
                }
            };
        text_1.addFocusListener(listener);
        text_2.addFocusListener(listener);
        text_3.addFocusListener(listener);
        combox_char.addItemListener(new ItemListener(){
                public void itemStateChanged(ItemEvent e){
                    compute();
                }
            });
    }

    private void compute(){
        long n1 = ((Long)text_1.getValue()).longValue();
        long n2 = ((Long)text_2.getValue()).longValue();
        switch (combox_char.getSelectedIndex()) {
        case 0:
            text_3.setValue(Long.valueOf(n1+n2));
            break;
        case 1:
            text_3.setValue(Long.valueOf(n1-n2));
            break;
        case 2:
            text_3.setValue(Long.valueOf(n1*n2));
            break;
        case 3:
            if (n2 != 0) {
                text_3.setValue(Long.valueOf(n1/n2));
            }
            break;
        default:
            break;
        }
    }

    public static void main(String args[])
    {
        java.awt.EventQueue.invokeLater(new java.lang.Runnable(){
                @Override public void run(){
                    new WangPeng();
                }
            });
    }
}