java swing FlowLayout 简易计算器布局，无功能实现

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

public class A_simple_caculator {

    private static void addComponentsToPane(Container pane) {

    	 JComboBox<String> box =  new JComboBox();
    	 box.addItem("+");
    	 box.addItem("-");
    	 box.addItem("*");
    	 box.addItem("/");
    	 
        pane.setLayout(new FlowLayout());  // content pane默认是BorderLayout,现在设置为Flowlayout
       
        pane.add(new JTextField(8)); 
        pane.add(box);
        pane.add(new JTextField(8));
        pane.add(new JButton("="));
        pane.add(new JTextField(8));

    }

    private static void createAndShowGUI() {

        //Create and set up the window.
        JFrame frame = new JFrame("A_simple_caculator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //Set up the content pane.
        addComponentsToPane(frame.getContentPane());
        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {              
        
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

public static void main(String args[]) {
        // Create the frame on the main thread
        // which is not event dispatching thread.
        createAndShowGUI(); 
    }          

//main函数这样写也可以成功运行，但是基于线程安全考虑，不能这样写。

参考资料 ： java swing编程介绍