Java实现简单计算器（四则运算，括号，浮点数）
用堆栈把输入的中缀表达式转化为后缀表达式，然后计算。用的是数据结构里的代码：表达式转换（中缀表达式转为后缀表达式）
import java.awt.Container;import java.awt.GridLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.util.Stack;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.JTextField;public class Main extends JFrame implements ActionListener {private String expression;//记录表达式private final String[] keys = {"(",")","CE","Back",//按键 "7","8","9"," ", "4","5","6","-", "1","2","3","*", ".","0","=","/"};private JTextField result = new JTextField("");//结果 private JButton[] buttons = new JButton[20];//按钮Main(){this.setTitle("简单计算器");this.setLocation(500,300);JPanel panel = new JPanel();//计算器布局panel.setLayout(new GridLayout(6,1));//布局分6行，第一行文本框panel.add(result);result.setFont(result.getFont().deriveFont((float)30));Container[] containers = new Container[5];for(int i=0 ; i<5; i ){containers[i] = new Container();containers[i].setLayout(new GridLayout(1,4));panel.add(containers[i]);}for(int i=0; i<buttons.length; i ){buttons[i] = new JButton(keys[i]);buttons[i].setFont(buttons[i].getFont().deriveFont((float)25));//设置字体大小containers[i/4].add(buttons[i]);buttons[i].addActionListener(this);}getContentPane().add(panel);expression="";//表达式为空}public static void main(String[] args) {Main calculator = new Main();calculator.setSize(400,400);//计算器长宽calculator.setVisible(true);}@Overridepublic void actionPerformed(ActionEvent e) {String action = e.getActionCommand();if(action.equals(keys[2])){//清空键cexpression = "";}else if(action.equals(keys[3])){//删除一个字符backexpression = expression.substring(0,expression.length()-1);}else if(action.equals(keys[18])){//计算结果=expression = Calculator.solve(expression);}else {expression = action;}result.setText(expression);}}class Calculator{public static String solve(String expression){//计算表达式double sum=0,flag=0;int top=-1;// 存数堆栈的指针//Stack<Double> stack1 = new Stack<Double>();Double类型的堆栈会损失精度，如存入2.1取出时就是2.0了double[] stack1 = new double[100];// 存数的堆栈,用数组模拟堆栈Stack<Character> stack2 = new Stack<Character>();//存运算符的堆栈for(int i=0 ; i<expression.length(); i ){char p = expression.charAt(i);flag = sum = 0;if(p >= '0' && p <= '9'){//存入数字while(true){p = expression.charAt(i);if(p == '.') flag = 0.1;else {if(flag == 0) sum = sum*10 (p-'0');else {//小数位处理sum = ((p-'0')*flag);flag *= 0.1;}}if(i 1<expression.length()&&((expression.charAt(i 1)>='0'&&expression.charAt(i 1)<='9')||expression.charAt(i 1)=='.')) i ;else {stack1[ top]=sum;break;}} }else {if(p=='(') stack2.push(p);else if(p == '*' || p == '/') {// 此时运算符是*或/时堆栈中优先级高的先计算while(stack2.size()>0 && (stack2.peek()=='*'||stack2.peek()=='/')) {double temp = compute(stack1[top--],stack1[top--],stack2.pop());stack1[ top] = temp;}stack2.push(p);//最后放入} else if(p==' '||p=='-') {// 此时运算符是 或-时括号之前的内容都取出来while(stack2.size()>0&&stack2.peek()!='(') {double temp=compute(stack1[top--],stack1[top--],stack2.pop());stack1[ top]=temp;}stack2.push(p);}else if(p==')') {// 此时运算符是)时堆栈内容都取出来while(stack2.size()>0&&stack2.peek()!='(') {double temp = compute(stack1[top--],stack1[top--],stack2.pop());stack1[ top] = temp;}stack2.pop();//取出左括号}}}while(stack2.size()>0) {//计算剩下的式子double temp=compute(stack1[top--],stack1[top--],stack2.pop());stack1[ top] = temp;}return "" stack1[top];//double类型强制转为String类型}public static double compute(double a,double b, char p) {//在函数中运算double sum = 0;if(p==' ') {sum = b a;}else if(p=='-') {//要注意用栈顶的数是被减数或者被除数sum = b-a;}else if(p=='*') {sum = b*a;}else if(p=='/') {sum = b/a;}return sum;}} 赞 (0)