Question

如何用Java编写四则运算程序？

利用java语言编写，写出算法及程序分析。

Answer 1

（首先建个类，把这些复制粘贴进去）
import java.awt.*;

import javax.swing.*;

public class F {
JFrame frame = new JFrame("计算机");

JPanel pl = new JPanel();

JPanel p2 = new JPanel();

static JTextField show = new JTextField();

static JButton b0 = new JButton("0");

static JButton b1 = new JButton("1");

static JButton b2 = new JButton("2");

static JButton b3 = new JButton("3");

static JButton b4 = new JButton("4");

static JButton b5 = new JButton("5");

static JButton b6 = new JButton("6");

static JButton b7 = new JButton("7");

static JButton b8 = new JButton("8");

static JButton b9 = new JButton("9");

JButton bjia = new JButton("+");

JButton bjian = new JButton("-");

JButton bcheng = new JButton("*");

JButton bchu = new JButton("/");

JButton bdian = new JButton(".");

JButton bdeng = new JButton("=");

JButton bqingchu = new JButton("清除");

public void y() {
pl.setLayout(new GridLayout(1, 1));
pl.add(show);
}

public void p() {
b1.addActionListener(new U());
b2.addActionListener(new U());
b3.addActionListener(new U());
b4.addActionListener(new U());
b5.addActionListener(new U());
b6.addActionListener(new U());
b7.addActionListener(new U());
b8.addActionListener(new U());
b9.addActionListener(new U());
b0.addActionListener(new U());

bjia.addActionListener(new Fu());
bjian.addActionListener(new Fu());
bcheng.addActionListener(new Fu());
bchu.addActionListener(new Fu());

bdeng.addActionListener(new Deng());
bqingchu.addActionListener(new Qing());

p2.setLayout(new GridLayout(6, 3));
p2.add(b1);
p2.add(b2);
p2.add(b3);
p2.add(b4);
p2.add(b5);
p2.add(b6);
p2.add(b7);
p2.add(b8);
p2.add(b9);
p2.add(b0);
p2.add(bjia);
p2.add(bjian);
p2.add(bcheng);
p2.add(bchu);
p2.add(bdian);
p2.add(bqingchu);
p2.add(bdeng);
}

public void o() {
frame.setLayout(new BorderLayout());
frame.add(pl, BorderLayout.NORTH);
frame.add(p2, BorderLayout.CENTER);
frame.setSize(400, 300);
frame.setVisible(true);

}

public static void main(String[] args) {
F f = new F();
f.y();
f.p();
f.o();

}

}

(再新建个类 把这些也复制粘贴进去)
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class U implements ActionListener {
public static String str = "";

public static String a = "";

public static String b = "";

public static String k = "";

public void actionPerformed(ActionEvent e) {
String w = e.getActionCommand();//字

if (k.equals("")) {
a += w;
F.show.setText(a);

} else {
b += w;
F.show.setText(b);
}

}

}

（再新建一个，把下面的复制粘贴）
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Deng implements ActionListener {

public void actionPerformed(ActionEvent e) {
int a = Integer.parseInt(U.a);
int b = Integer.parseInt(U.b);
int c = 0;
if (U.k.equals("+")) {
c = a + b;

} else

if (U.k.equals("-")) {
c = a - b;

} else

if (U.k.equals("*")) {
c = a * b;

} else

if (U.k.equals("/")) {
c = a / b;

} else {

}

String d = String.valueOf(c);
F.show.setText(d);
U.a = d;
U.b = "";
U.k = "";
}
}

（在建一个 复制粘贴）
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Fu implements ActionListener {

public void actionPerformed(ActionEvent e) {
String a = e.getActionCommand();//字
U.k = a;

}

}

（在建一个）
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Qing implements ActionListener {

public void actionPerformed(ActionEvent e) {
U.a = "";
U.b = "";
U.k = "";
F.show.setText("");

}

}

Answer 2

提取运算数字和运算符号和运算结果三个对象,设计原型界面,主要运用SWITCH判断运算符号,分别调用其对象所对应的方法,传入运算数字,把结果返回给运算结果,向界面输出运算结果..搞定