java swing 简易flowLayout 计算器 带功能实现 支持小数

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JTextField;

class sss implements ActionListener{
   JTextField text1,text2,text3;
   JButton button;
   ActionListener bl;
   
   JComboBox box;
   double number1,number2;
    sss(){
        JFrame frame = new JFrame("ButtonDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new FlowLayout());  
        // 等价于frame.getContentPane().setLayout(new FlowLayout());
        text1 = new JTextField(8);
    	text2 = new JTextField(8);
    	text3 = new JTextField(8);
    	button =  new JButton("=");
        
        String[] arr = new String[] {"+","-","*","/"} ;
        box =  new JComboBox();  
        for(int i = 0; i<arr.length;i++) {
       	box.addItem(arr[i]);  
        }
        button.addActionListener(this);
        text1.addActionListener(this);
        text2.addActionListener(this);
        text3.addActionListener(this);
        
        frame.add(text1);   
        frame.add(box);  
        frame.add(text2);  
        frame.add(button);  
        frame.add(text3);  
        
        frame.pack();
        frame.setVisible(true);
 
   
    }
    
    public static void main(String[] args) {        
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new sss();
            }
        });
    }
   
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub
		
		String str1 = text1.getText();
		number1 = Double.valueOf(str1);
		String str2 = text2.getText();
		number2 = Double.valueOf(str2);
		String fuhao = (String) box.getSelectedItem();
		
		if(e.getSource().equals(button)){
			if(fuhao == "+") {
				double result  = number1 + number2;
	             text3.setText(""+result);
			}
			 
			if(fuhao == "-") {
				double result  = number1 - number2;
	             text3.setText(""+result);
			}
			
			if(fuhao == "*") {
				double result  = number1 * number2;
	             text3.setText(""+result);
			}
			
			if(fuhao == "/") {
				double result  = number1 / number2;
	             text3.setText(""+result);
			}
		}
		
		
		
	}
}