对输入字符串进行求值java代码

好的，我可以帮助您实现对字符串的求值。以下是示例Java代码：

import java.util.Stack;

public class EvaluateString {
    public static int evaluate(String expression) {
        char[] tokens = expression.toCharArray();

        //存放数值的栈
        Stack<Integer> values = new Stack<Integer>();

        //存放运算符的栈
        Stack<Character> operators = new Stack<Character>();

        for (int i = 0; i < tokens.length; i++) {

            //如果是空格则忽略
            if (tokens[i] == ' ')
                continue;

            //如果是数字则将它存入数值栈
            if (tokens[i] >= '0' && tokens[i] <= '9') {
                StringBuffer sbuf = new StringBuffer();
                //可能存在多位数字，需拼接
                while (i < tokens.length && tokens[i] >= '0' && tokens[i] <= '9')
                    sbuf.append(tokens[i++]);
                values.push(Integer.parseInt(sbuf.toString()));
                i--;
            }

            //如果是左括号，将其存入运算符栈
            else if (tokens[i] == '(')
                operators.push(tokens[i]);

            //如果是右括号，则弹出栈顶的运算符并将两个数值栈的栈顶元素进行计算
            else if (tokens[i] == ')') {
                while (operators.peek() != '(')
                    values.push(applyOp(operators.pop(), values.pop(), values.pop()));
                operators.pop();
            }

            //如果是运算符，则弹出栈顶的运算符进行计算
            else if (tokens[i] == '+' || tokens[i] == '-' ||
                     tokens[i] == '*' || tokens[i] == '/') {
                while (!operators.empty() && hasPrecedence(tokens[i], operators.peek()))
                    values.push(applyOp(operators.pop(), values.pop(), values.pop()));
                operators.push(tokens[i]);
            }
        }

        //计算剩下在栈中的运算符
        while (!operators.empty())
            values.push(applyOp(operators.pop(), values.pop(), values.pop()));

        //返回运算结果
        return values.pop();
    }

    //计算两个数的运算结果
    public static int applyOp(char op, int b, int a) {
        switch (op) {
        case '+':
            return a + b;
        case '-':
            return a - b;
        case '*':
            return a * b;
        case '/':
            if (b == 0)
                throw new UnsupportedOperationException("除数不能为0");
            return a / b;
        }
        return 0;
    }

    //判断两个运算符的优先级
    public static boolean hasPrecedence(char op1, char op2) {
        if (op2 == '(' || op2 == ')')
            return false;
        if ((op1 == '*' || op1 == '/') && (op2 == '+' || op2 == '-'))
            return false;
        else
            return true;
    }

    public static void main(String[] args) {
        String expression = "10 + 2 * 6";
        System.out.println(evaluate(expression));

        expression = "100 * 2 + 12";
        System.out.println(evaluate(expression));

        expression = "100 * ( 2 + 12 )";
        System.out.println(evaluate(expression));
        
        expression = "( 16 + 3 ) * 2 / 11";
        System.out.println(evaluate(expression));
    }
}

该代码实现了基本的四则运算，包括加、减、乘、除和括号。您可以在 `main` 函数中尝试不同的表达式并查看运算结果。