在组件中显示信息——图形设计程序

public class NotHelloWorld {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run(){
                JFrame frame = new NotHelloWorldFrame();
                frame.setTitle("NotHelloWorld");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }
}

程序主体，在事件队列中创建一个将运行的接口。设置窗口的标题和退出按钮。
JFrame frame = new NotHelloWorldFrame(); 创建一个新的窗口类。

class NotHelloWorldFrame extends JFrame{
    private static final long serialVersionUID = 1L;

    public NotHelloWorldFrame() {
        add(new NotHelloWorldComonent());
        pack();		//只使用首选大小
    }
}

在新的窗口类NotHelloWorldFrame里面，添加组件NotHelloWorldComonent到内容窗格里。

class NotHelloWorldComonent extends JComponent{
    private static final long serialVersionUID = 1L;
    
    public static final int Message_X = 75;
    public static final int Message_Y = 100;

    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHT = 200;

    public void paintComponent(Graphics g){
        g.drawString("I am Zhang JunFeng", Message_X, Message_Y);
    }

    public Dimension getPreferredSize() {return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT);} //
}

定义组件，组件设置了要显示消息的窗口位置，窗口的位置，消息的内容。最后一行设置返回组件的首选大小。

---

package notHelloWorld;

import javax.swing.*;
import java.awt.*;

/**
 * @version 2020/2/1
 */
public class NotHelloWorld {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run(){
                JFrame frame = new NotHelloWorldFrame();
                frame.setTitle("NotHelloWorld");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }
}

/**
 * Frame和NotHelloWorld的接口
 */
class NotHelloWorldFrame extends JFrame{
    private static final long serialVersionUID = 1L;

    public NotHelloWorldFrame() {
        add(new NotHelloWorldComonent());   //添加一个内容窗格
        pack();
    }
}

/**
 * 组件，设置内容窗格的属性
 */
class NotHelloWorldComonent extends JComponent{
    private static final long serialVersionUID = 1L;
    
    public static final int Message_X = 75;
    public static final int Message_Y = 100;

    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHT = 200;

    public void paintComponent(Graphics g){
        g.drawString("I am Zhang JunFeng", Message_X, Message_Y);
    }

    public Dimension getPreferredSize() {return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT);}  //返回组件的首选大小
}