Java计算器设计实现

需求分析

• 目的是实现一个基于Java的可以求解带括号加减乘除表达式的带界面的计算器。
• 需要知道的Java技术：Java Swing（Java图形界面设计）、Java集合（栈）、lambda表达式、Java基础等。

设计思路

1. 实现一个Java计算器界面类
2. 实现一个Java计算带括号加减乘除表达式的类
3. 实现主函数调用

设计实现

• Java计算器项目结构：
  
  Calculator类为计算器界面设计、Calculate类为计算带括号加减乘除表达式的类，Main函数为项目程序入口。
• Java计算器界面设计实现代码：

package Calculator;

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Calculator extends JFrame{
		
	private double result=0;
	private int count=0;
	
	public Calculator() {
		this.setSize(330,399);		
		this.setTitle("计算器");		
		init();
//		this.pack();
		this.setVisible(true);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);		
	}
	
	public void init() {//初始化界面
		
		this.setLayout(new BorderLayout()); //总体布局为边框式布局
		
		/*
		 * 总体边框式布局north放置文本框
		 */		
		JTextField textField=new JTextField();
		textField.disable();
		textField.setPreferredSize(new Dimension(this.getWidth(),50));
		this.add(textField,BorderLayout.NORTH);

		/*	
		 * 总体边框式布局center放置@panel(边框式布局）
		 * @panel边框式布局north放置@panelN(网格布局)
		 * @panel边框式布局center放置@panelC(卡片式布局)
		 * @panelC卡片来切换@panel0(标准)和@panel1(科学)两种模式
		 * @panel0,@panel1均为网格布局
		 */					
		JPanel panel=new JPanel();
		panel.setLayout(new BorderLayout());
		this.add(panel, BorderLayout.CENTER);
		
		JPanel panelN=new JPanel();
		panelN.setLayout(new GridLayout(1,6));
		JButton MC=new JButton("MC");
		JButton MR=new JButton("MR");
		JButton M0=new JButton("M+");
		JButton M1=new JButton("M-");
		JButton MS=new JButton("MS");
		JButton M=new JButton("M");
		panelN.add(MC);panelN.add(MR);panelN.add(M0);
		panelN.add(M1);panelN.add(MS);panelN.add(M);
		panel.add(panelN,BorderLayout.NORTH);
		
		CardLayout cardLayout=new CardLayout();
		JPanel panelC=new JPanel();
		panelC.setLayout(cardLayout);
		
		JPanel panel0=new JPanel();
		panel0.setLayout(new GridLayout(6,4));
		JButton[] standredButton=new JButton[24];
		String str[]={"%","√","x²","1/x",
				"CE","C","×","/",
				"7","8","9","*",
				"4","5","6","-",
				"1","2","3","+",
				"±","0",".","="	
		};
		for(int i=0;i<standredButton.length;i++) {
			standredButton[i]=new JButton(str[i]);
			String text=standredButton[i].getText();
			standredButton[i].addActionListener(new ActionListener() {
				
				@Override
				public void actionPerformed(ActionEvent e) {
					// TODO Auto-generated method stub
					if(text.equals("CE")||text.equals("C")) {
						textField.setText("");
					}
					else if(text.equals("=")) {
						String expression=textField.getText();
						Calculate cal=new Calculate();
						textField.setText(cal.evaluateExpression(expression)+"");
					}
					else if(text.equals("%")) {
						
					}
					else if(text.equals("√")) {
						result=Double.parseDouble(textField.getText());
						result=Math.sqrt(result);
						textField.setText(result+"");
					}
					else if(text.equals("x²")) {
						result=Double.parseDouble(textField.getText());
						result*=result;
						textField.setText(result+"");
					}
					else if(text.equals("1/x")) {
						result=Double.parseDouble(textField.getText());
						result=1/result;
						textField.setText(result+"");
					}
					else if(text.equals("±")) {
						if(count==0) {
							textField.setText(textField.getText()+"-");
							count=1;
						}
						else {
							textField.setText(textField.getText()+"+");
							count=0;
						}
					}
					else if(text.equals("×")) {
						textField.setText(textField.getText().substring(0, textField.getText().length()-1));
					}
					else {
						textField.setText(textField.getText()+text);
					}
									
				}
				
			}
			
			);
			panel0.add(standredButton[i]);
		}
		panelC.add(panel0);
		
		JPanel panel1=new JPanel();
		panel1.setLayout(new GridLayout(7,5));
		JButton scienceButton[]=new JButton[35];
		String str1[]= {
		"x²","x^y","sin","cos","tan",
		"√","10^x","log","Exp","Mod",
		"↑","CE","C","×","/",
		"π","7","8","9","*",
		"n!","4","5","6","-",
		"±","1","2","3","+",
		"(",")","0",".","="				
		};
		for(int i=0;i<str1.length;i++) {
			scienceButton[i]=new JButton(str1[i]);
			//scienceButton[i].addActionListener();
			panel1.add(scienceButton[i]);
		}
		panelC.add(panel1);
			
		panel.add(panelC,BorderLayout.CENTER);
		
		/*
		 * 菜单	
		 */
		JMenuBar menuBar=new JMenuBar();
		this.setJMenuBar(menuBar);
		JMenu modelMenu=new JMenu("模式");
		menuBar.add(modelMenu);
		JMenuItem standred=new JMenuItem("标准");		
		standred.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				// TODO Auto-generated method stub
				cardLayout.first(panelC);
			}		
		});
		modelMenu.add(standred);
		JMenuItem science=new JMenuItem("科学");
		science.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				// TODO Auto-generated method stub
				cardLayout.last(panelC);
			}			
		});
		modelMenu.add(science);
		
	}
/*
	private class ButtonAction implements ActionListener{

		@Override
		public void actionPerformed(ActionEvent e) {
			// TODO Auto-generated method stub
					
		}		
	}
*/
}

• Java计算带括号加减乘除表达式类的实现：

package Calculator;

import java.util.*;

/*
*使用此类直接调用evaluateExpression方法即可，传入需计算的表达式，返回计算结果
*/
public class Calculate {
    //这个函数的作用就是使用空格分割字符串，以便后面使用分割函数使得将字符串分割成数组
    public String insetBlanks(String s) {
        String result = "";
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == '(' || s.charAt(i) == ')' ||
                    s.charAt(i) == '+' || s.charAt(i) == '-'
                    || s.charAt(i) == '*' || s.charAt(i) == '/')
                result += " " + s.charAt(i) + " ";
            else
                result += s.charAt(i);
        }
        return result;
    }

    public double evaluateExpression(String expression) {
        Stack<Double> operandStack = new Stack<>();
        Stack<Character> operatorStack = new Stack<>();
        expression = insetBlanks(expression);
        String[] tokens = expression.split(" ");
        for (String token : tokens) {
            if (token.length() == 0)   //如果是空格的话就继续循环，什么也不操作
                continue;
            //如果是加减的话，因为加减的优先级最低，因此这里的只要遇到加减号，无论操作符栈中的是什么运算符都要运算
            else if (token.charAt(0) == '+' || token.charAt(0) == '-') {
                //当栈不是空的，并且栈中最上面的一个元素是加减乘除的人任意一个
                while (!operatorStack.isEmpty()&&(operatorStack.peek() == '-' || operatorStack.peek() == '+' || operatorStack.peek() == '/' || operatorStack.peek() == '*')) {
                    processAnOperator(operandStack, operatorStack);   //开始运算
                }
                operatorStack.push(token.charAt(0));   //运算完之后将当前的运算符入栈
            }
            //当前运算符是乘除的时候，因为优先级高于加减，因此要判断最上面的是否是乘除，如果是乘除就运算，否则的话直接入栈
            else if (token.charAt(0) == '*' || token.charAt(0) == '/') {
                while (!operatorStack.isEmpty()&&(operatorStack.peek() == '/' || operatorStack.peek() == '*')) {
                    processAnOperator(operandStack, operatorStack);
                }
                operatorStack.push(token.charAt(0));   //将当前操作符入栈
            }
            //如果是左括号的话直接入栈，什么也不用操作,trim()函数是用来去除空格的，由于上面的分割操作可能会令操作符带有空格
            else if (token.trim().charAt(0) == '(') {
                operatorStack.push('(');
            }
            //如果是右括号的话，清除栈中的运算符直至左括号
            else if (token.trim().charAt(0) == ')') {
                while (operatorStack.peek() != '(') {
                    processAnOperator(operandStack, operatorStack);    //开始运算
                }
                operatorStack.pop();   //这里的是运算完之后清除左括号
            }
            //这里如果是数字的话直接如数据的栈
            else {
                operandStack.push(Double.parseDouble(token));   //将数字字符串转换成数字然后压入栈中
            }
        }
        //最后当栈中不是空的时候继续运算，知道栈中为空即可
        while (!operatorStack.isEmpty()) {
            processAnOperator(operandStack, operatorStack);
        }
        return operandStack.pop();    //此时数据栈中的数据就是运算的结果
    }

    //这个函数的作用就是处理栈中的两个数据，然后将栈中的两个数据运算之后将结果存储在栈中
    public void processAnOperator(Stack<Double> operandStack, Stack<Character> operatorStack) {
        char op = operatorStack.pop();  //弹出一个操作符
        Double op1 = operandStack.pop();  //从存储数据的栈中弹出连个两个数用来和操作符op运算
        Double op2 = operandStack.pop();
        if (op == '+')  //如果操作符为+就执行加运算
            operandStack.push(op1 + op2);
        else if (op == '-')
            operandStack.push(op2 - op1);   //因为这个是栈的结构，自然是上面的数字是后面的，因此用op2-op1
        else if (op == '*')
            operandStack.push(op1 * op2);
        else if (op == '/')
            operandStack.push(op2 / op1);
    }
}

• 主函数：

package Calculator;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Calculator calculator=new Calculator();
	}

}

设计实现展示

• 可以随意缩小放大界面，界面部件会跟随界面大小自适应调整。

其他功能

• 目前实现了标准型计算，科学型计算更加复杂，实现了界面，没有计算功能，后续可能会继续开发，敬请期待。