java实现逆波兰表达式算法，java波兰表达式,import java.

java实现逆波兰表达式算法，java波兰表达式,import java.

import java.util.ArrayList;import java.util.List;public class MyStack {    private List<String> l;    private int size;    public String top;    public MyStack() {        l = new ArrayList<String>();        size = 0;        top = null;    }    public int size() {        return size;    }    public void push(String s) {        l.add(s);        top = s;        size++;    }    public String pop() {        String s = l.get(size - 1);        l.remove(size - 1);        size--;        top = size == 0 ? null : l.get(size - 1);        return s;    }}

import java.util.ArrayList;import java.util.List;public class Nbl {    private static MyStack ms1 = new MyStack();//生成逆波兰表达式的栈    private static MyStack ms2 = new MyStack();//运算栈    /**     * 将字符串转换为中序表达式     */    public static List<String> zb(String s) {        List<String> ls = new ArrayList<String>();//存储中序表达式        int i = 0;        String str;        char c;        do {            if ((c = s.charAt(i)) < 48 || (c = s.charAt(i)) > 57) {                ls.add("" + c);                i++;            } else {                str = "";                while (i < s.length() && (c = s.charAt(i)) >= 48                        && (c = s.charAt(i)) <= 57) {                    str += c;                    i++;                }                ls.add(str);            }        } while (i < s.length());        return ls;    }    /**     * 将中序表达式转换为逆波兰表达式     */    public static List<String> parse(List<String> ls) {        List<String> lss = new ArrayList<String>();        for (String ss : ls) {            if (ss.matches("\\d+")) {                lss.add(ss);            } else if (ss.equals("(")) {                ms1.push(ss);            } else if (ss.equals(")")) {                while (!ms1.top.equals("(")) {                    lss.add(ms1.pop());                }                ms1.pop();            } else {                while (ms1.size() != 0 && getValue(ms1.top) >= getValue(ss)) {                    lss.add(ms1.pop());                }                ms1.push(ss);            }        }        while (ms1.size() != 0) {            lss.add(ms1.pop());        }        return lss;    }    /**     * 对逆波兰表达式进行求值     */    public static int jisuan(List<String> ls) {        for (String s : ls) {            if (s.matches("\\d+")) {                ms2.push(s);            } else {                int b = Integer.parseInt(ms2.pop());                int a = Integer.parseInt(ms2.pop());                if (s.equals("+")) {                    a = a + b;                } else if (s.equals("-")) {                    a = a - b;                } else if (s.equals("*")) {                    a = a * b;                } else if (s.equals("\\")) {                    a = a / b;                }                ms2.push("" + a);            }        }        return Integer.parseInt(ms2.pop());    }    /**     * 获取运算符优先级     * +,-为1 *,/为2 ()为0     */    public static int getValue(String s) {        if (s.equals("+")) {            return 1;        } else if (s.equals("-")) {            return 1;        } else if (s.equals("*")) {            return 2;        } else if (s.equals("\\")) {            return 2;        }        return 0;    }    public static void main(String[] args) {        System.out.println(jisuan(parse(zb("0-8+((1+2)*4)-3+(2*7-2+2)"))));    }}