怎么用过Java写个简单的计算器
如何用过Java写个简单的计算器？
就是从键盘先输入个运算符号，判断是加法、减法还是乘法、除法，然后在用import java.util.*; 的Scanner a=new Scanner(System.in); Scanner b=new Scanner(System.in);输入两个值，将运算结果输出到int c。
可是怎么输入字符呢？
------解决思路----------------------
如果你是指这样的话.
------解决思路----------------------
写了一个，没考虑精度要求
------解决思路----------------------
楼主是switch...case这个语法没搞懂，我想里面的代码按理没没有什么难度了
------解决思路----------------------
你得把symbol定义为String呀，另外你可以试试用Application
------解决思路----------------------
其实计算器不算是一个简单的练习
------解决思路----------------------
严谨的话，还要考虑精度问题。
就是从键盘先输入个运算符号，判断是加法、减法还是乘法、除法，然后在用import java.util.*; 的Scanner a=new Scanner(System.in); Scanner b=new Scanner(System.in);输入两个值，将运算结果输出到int c。
可是怎么输入字符呢？
/**
模拟计算器
@author 赵鸿洋
@version 1.0
*/
import java.util.*;
public class calculator {
public static void main(String[] args){
System.out.println("请输入一个运算符号（加、减、乘、除）");
Scanner symbol = new Scanner(System.in);
/*就是从这网上不懂*/
switch(symbol){
case '+' : Scanner a = new Scanner(System.in);
Scanner b = new Scanner(System.in);
int c = a + b;
System.out.println(c);
break;
case '-' :Scanner a = new Scanner(System.in);
Scanner b = new Scanner(System.in);
int c = a - b;
System.out.println(c);
break;
case '*' :Scanner a = new Scanner(System.in);
Scanner b = new Scanner(System.in);
int c = a * b;
System.out.println(c);
break;
case '/': Scanner a = new Scanner(System.in);
Scanner b = new Scanner(System.in);
int c = a / b;
System.out.println(c);
break;
default :System.out.println("非法运算符");
break;
}
}
}
------解决思路----------------------
import java.util.*;
public class calculator {
public static void main(String[] args){
System.out.println("请输入一个运算符号（加、减、乘、除）");
Scanner in=new Scanner(System.in);
String symbol=in.next();
int a =in.nextInt();
int b=in.nextInt();
in.close();
int res;
/*就是从这网上不懂*/
switch(symbol.toString()){
case "+":
res = a + b;
break;
case "-" :
res = a - b;
break;
case "*" :
res = a * b;
break;
case "/":
res = a / b;
break;
default :System.out.println("非法运算符");
//in.close();
return;
}
System.out.println(res);
//in.close();
}
}
如果你是指这样的话.
------解决思路----------------------
写了一个，没考虑精度要求
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
public class Calculator extends JFrame {
/**
*
*/
private static final long serialVersionUID = 7749672600888030905L;
/**
* result 用于显示结果的标签
* flag 表示是否进行新的运算
* lastCommand 记录上一次的运算符
* lastNum 记录上次运算的结果
*/
private JLabel result;
private boolean flag = true;
private String lastCommand = "=";
private double lastNum = 0;
/**
* 构造器
*/
public Calculator() {
layoutCalculator();
add(createContent());
}
private void layoutCalculator() {
setSize(200, 200);
setTitle("Calculator 1.0");
setResizable(false);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
/**
* 创建内容面板
* @return
*/
private JPanel createContent() {
JPanel content = new JPanel(new BorderLayout());
result = new JLabel("0", SwingConstants.RIGHT);
content.add(BorderLayout.NORTH, result);
content.add(BorderLayout.CENTER, createButtonPanel());
return content;
}
/**
* 创建一个网格面板
* @return
*/
private JPanel createButtonPanel() {
JPanel panel = new JPanel(new GridLayout(4, 4));
panel.add(createButton("7", new NumberActionListener("7")));
panel.add(createButton("8", new NumberActionListener("8")));
panel.add(createButton("9", new NumberActionListener("9")));
panel.add(createButton("/", new CommandActionListener("/")));
panel.add(createButton("4", new NumberActionListener("4")));
panel.add(createButton("5", new NumberActionListener("5")));
panel.add(createButton("6", new NumberActionListener("6")));
panel.add(createButton("*", new CommandActionListener("*")));
panel.add(createButton("1", new NumberActionListener("1")));
panel.add(createButton("2", new NumberActionListener("2")));
panel.add(createButton("3", new NumberActionListener("3")));
panel.add(createButton("-", new CommandActionListener("-")));
panel.add(createButton("0", new NumberActionListener("0")));
panel.add(createButton(".", new NumberActionListener(".")));
panel.add(createButton("=", new CommandActionListener("=")));
panel.add(createButton("+", new CommandActionListener("+")));
return panel;
}
/**
* 创建一个按钮
* @param name
* @param listener
* @return
*/
private JButton createButton(String name, ActionListener listener) {
JButton button = new JButton(name);
button.addActionListener(listener);
return button;
}
/**
* 数字按钮的监听器类
* @author Administrator
*
*/
private class NumberActionListener implements ActionListener {
private String name;
public NumberActionListener(String name) {
super();
this.name = name;
}
@Override
public void actionPerformed(ActionEvent e) {
if (flag) {
result.setText(name);
flag = false;
} else {
result.setText(result.getText() + name);
}
}
}
/**
* 命令按钮的监听器类
* @author Administrator
*
*/
private class CommandActionListener implements ActionListener {
private String name;
public CommandActionListener(String name) {
super();
this.name = name;
}
@Override
public void actionPerformed(ActionEvent e) {
if (flag) {
if (name.equals("-")) {
result.setText(name);
flag = false;
} else{
lastCommand = name;
}
} else {
calculate(Double.parseDouble(result.getText()));
lastCommand = name;
flag = true;
}
}
}
/**
* 运算方法
* @param d
*/
public void calculate(double d) {
if (lastCommand.equals("+")) {
lastNum += d;
} else if (lastCommand.equals("-")) {
lastNum -= d;
} else if (lastCommand.equals("*")) {
lastNum *= d;
} else if (lastCommand.equals("/")) {
lastNum /= d;
} else if (lastCommand.equals("=")) {
lastNum = d;
}
result.setText(String.valueOf(lastNum));
}
public static void main(String[] args) {
Calculator cal = new Calculator();
cal.setVisible(true);
}
}
------解决思路----------------------
楼主是switch...case这个语法没搞懂，我想里面的代码按理没没有什么难度了
------解决思路----------------------
你得把symbol定义为String呀，另外你可以试试用Application
------解决思路----------------------
其实计算器不算是一个简单的练习
------解决思路----------------------
严谨的话，还要考虑精度问题。