Java基础题目

package com.test.day0308;

import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

class Rect {
    int length;
    int width;
    public Rect(int length, int width) {
        this.length = length;
        this.width = width;
    }
    public int getLen() {
        return 2 * (width + length);
    }
    public int getArea() {
        return length * width;
    }
}
public class TestRect extends KeyAdapter {
    private static JTextField[] txts = new JTextField[4];
    private void init() {
        JFrame jframe = new JFrame();
        jframe.setBounds(400, 400, 240, 140);
        jframe.setVisible(true);
        jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jframe.setLayout(null);
        jframe.setResizable(false);
        String[] lblStrs = {"宽:", "高:", "周长:", "面积:"};
        for (int i = 0; i < lblStrs.length; i++) {
            JLabel lbl = new JLabel(lblStrs[i]);
            lbl.setBounds(20, 20 * (i + 1), 40, 18);
            jframe.add(lbl);
            txts[i] = new JTextField();
            jframe.add(txts[i]);
            txts[i].setBounds(80, 20 * (i + 1), 100, 20);
            if (i >= 2) {
                txts[i].setEditable(false);
            } else {
                txts[i].addKeyListener(TestRect.this);
            }
        }
        jframe.repaint();
    }
    public static void main(String[] args) {
        new TestRect().init();
    }
    @Override
    public void keyReleased(KeyEvent e) {
        int width = -1;
        int height = -1;   
        if (txts[0].getText().matches("[0-9]+")) {
            width = Integer.valueOf(txts[0].getText());
        }
        if (txts[1].getText().matches("[0-9]+")) {
            height = Integer.valueOf(txts[1].getText());
        }
        txts[2].setText("?");
        txts[3].setText("?");
        if (width >= 0 && height >= 0) {
            Rect rect = new Rect(height, width);
            txts[2].setText(rect.getLen()+"");
            txts[3].setText(rect.getArea()+"");
        }
    }
}