Dijkstra双栈表达式求值算法

public class expression {
	public static void main(String[] args) {
		Stack<Character> ops = new Stack<Character>();//运算符栈
		Stack<Integer> vals = new Stack<Integer>();//操作数栈
		String str = "(1+((2+3)*(4*5)))";
		for(int i=0;i<str.length();i++) {
			char ch = str.charAt(i);
			if(ch == '(');//忽略左括号
			else if(ch == '+' || ch == '-' || ch == '*' || ch =='/') ops.push(ch);//操作数压入操作数栈
			else if(ch == ')') {
				char op = ops.pop();
				int v = vals.pop();
				if(op == '+')	v = vals.pop() + v;
				if(op == '-')	v = vals.pop() - v;
				if(op == '*')	v = vals.pop() * v;
				if(op == '/')	v = vals.pop() / v;
				vals.push(v);
			}
			else vals.push(Integer.parseInt(String.valueOf(ch)));//运算符压入运算符栈
		}
		System.out.println(vals.pop());
	}
}