学步园

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

public class Calculator implements ActionListener{
    JFrame jf = new JFrame("Calculator by chenyadong");
    JTextField tf = new JTextField();//输入数字的区域
    
double data;//用于记录输入符号前的数据
    String operator;//符号位
boolean clickable = true, clear = true;// clickable 用于判定"."，clear用于判定是否点击符号位 用于清屏
    
public void init() {
        jf.setSize(300,200);//设置大小
        jf.setVisible(true);//设置为可视
        
        Container c = jf.getContentPane();//得到JFrame的内容窗格对象
    
        tf.setHorizontalAlignment(JTextField.RIGHT);//右对齐    
        c.add(tf, "North");

        JPanel pn1 = new JPanel(new GridLayout(4,4));//运算界面
        c.add(pn1, "Center");

        JButton b = new JButton("7");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("8");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("9");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("/");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("4");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("5");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("6");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("*");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("1");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("2");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("3");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("-");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("0");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton(".");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("=");
        b.addActionListener(this);
        pn1.add(b);
        b = new JButton("+");
        b.addActionListener(this);
        pn1.add(b);
    }

public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
        String temp = e.getActionCommand();//获取按钮的标签
        if (temp == "0") {
if(clear == false) {//判断是否点击了符号位
                tf.setText("");
            }
            tf.setText(tf.getText() + "0");
        }
if (temp == "1") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "1");
            clear = true;
        }
if (temp == "1") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "1");
            clear = true;
        }
if (temp == "2") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "2");
            clear = true;
        }
if (temp == "3") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "3");
            clear = true;
        }
if (temp == "4") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "4");
            clear = true;
        }
if (temp == "5") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "5");
            clear = true;
        }
if (temp == "6") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "6");
            clear = true;
        }
if (temp == "7") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "7");
            clear = true;
        }
if (temp == "8") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "8");
            clear = true;
        }
if (temp == "9") {
if(clear == false) {
                tf.setText("");
            }
            tf.setText(tf.getText() + "9");
            clear = true;
        }

if (temp == ".") {
            clickable = true;
for (int i = 0; i < tf.getText().length(); i++) {//遍历判断是否已有"."
                if (tf.getText().charAt(i) == '.') {
                    clickable = false;
break;
                }
            }
if (clickable == true) {
                tf.setText(tf.getText() + ".");
            }
        }

try {
if (temp == "+") {
                data = Double.parseDouble(tf.getText());//字符串解析成double类型
                operator = "+";
                clear = false;
            }
if (temp == "-") {
                data = Double.parseDouble(tf.getText());
                operator = "-";
                clear = false;
            }
if (temp == "*") {
                data = Double.parseDouble(tf.getText());
                operator = "*";
                clear = false;
            }
if (temp == "/") {
                data = Double.parseDouble(tf.getText());
                operator = "/";
                clear = false;
            }

if (temp == "=") {
double data2 = Double.parseDouble(tf.getText());
                tf.setText("");
if (operator == "+") 
                    tf.setText(data + data2 + "");// + "" 变为String类型
                if (operator == "-") 
                    tf.setText(data - data2 + "");
if (operator == "*") 
                    tf.setText(data * data2 + "");
if (operator == "/") 
                    tf.setText(data / data2 + "");
                clear = false;
            }
        } catch (Exception ee) {
            System.out.println("运算时，首先输入数字");
            clear = false;
        }

    }

public static void main(String args[]) {
new Calculator().init();
    }

}