java实现计算器括号功能代码

import java.util.Stack;
import java.util.regex.*;

public class StringToArithmetic {
private StringToArithmetic() {
}

/**
* 给出一个算术表达式，返回结果。 例如 (5+8+10)*1，返回23
*
* @param string
*/
public static double stringToArithmetic(String string) {
return suffixToArithmetic(infixToSuffix(string));
}

/**
* 中缀表达式转后缀表达式
* 只处理了+,-,*,/和括号，没有处理负号及其它运算符，也没对前缀表达式验证。
* 如要处理负号，可对表达式进行预转义处理，当下面条件成立时，将负号换成单目运算符"!"
* infix.charAt[i]=='-'&&( i==0||infix.charAt[i-1]=='(')
*/
private static String infixToSuffix(String infix) {
Stack stack = new Stack();
String suffix = "";
int length = infix.length();
for (int i = 0; i < length; i++) {
Character temp;
char c = infix.charAt(i);
switch (c) {
// 忽略空格
case ' ':
break;
// 碰到'('，push到栈
case '(':
stack.push(c);
break;
// 碰到'+''-'，将栈中所有运算符弹出，送到输出队列中
case '+':
case '-':
while (stack.size() != 0) {
temp = stack.pop();
if (temp == '(') {
stack.push('(');
break;
}
suffix += " " + temp;
}
stack.push(c);
suffix += " ";
break;
// 碰到'*''/'，将栈中所有乘除运算符弹出，送到输出队列中
case '*':
case '/':
while (stack.size() != 0) {
temp = stack.pop();
if (temp == '(' || temp == '+' || temp == '-') {
stack.push(temp);
break;
} else {
suffix += " " + temp;
}
}
stack.push(c);
suffix += " ";
break;
// 碰到右括号，将靠近栈顶的第一个左括号上面的运算符全部依次弹出，送至输出队列后，再丢弃左括号
case ')':
while (stack.size() != 0) {
temp = stack.pop();
if (temp == '(')
break;
else
suffix += " " + temp;
}
//suffix += " ";
break;
default:

suffix += c;
}
}
while (stack.size() != 0)
suffix += " " + stack.pop();
return suffix;
}

public static void main(String args[]){
System.out.println(infixToSuffix("3+(2-5)*6/3"));
System.out.println(stringToArithmetic("3+(2-5)*6/3"));
}

/**
* 通过后缀表达式求出算术结果
*
* @param String
* postfix
* @return double
*/
private static double suffixToArithmetic(String postfix) {
Pattern pattern = https://www.doczj.com/doc/185594802.html,pile("\\d+||(\\d+\\.\\d+)"); // 匹配数字
String strings[] = postfix.split(" ");
for (int i = 0; i < strings.length; i++)
strings[i].trim();
Stack stack = new Stack();
for (int i = 0; i < strings.length; i++) {

if (strings[i].equals(""))
continue;
if ((pattern.matcher(strings[i])).matches()) {

stack.push(Double.parseDouble(strings[i]));
} else {

double y = stack.pop();
double x = stack.pop();
stack.push(caculate(x, y, strings[i]));
}
}
return stack.pop();


}

private static double caculate(double x, double y, String simble) {
if (simble.trim().equals("+"))
return x + y;
if (simble.trim().equals("-"))
return x - y;
if (simble.trim().equals("*"))
return x * y;
if (simble.trim().equals("/"))
return x / y;
return 0;
}
}