java計算工具類 ：中綴表達式轉波蘭後綴式並計算出結果

本文原算法原文來自https://blog.csdn.net/jdbfvhxx/article/details/98441580 by @ ^ @
對原算法增加了取模運算，並且做了適當的調整，每次運算之後自動清空棧和隊列，使其更容易被重複使用：
工具類ReversePolishMultiCalc源碼如下（下面有使用方法）：

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Stack;
import java.util.regex.Pattern;

public class ReversePolishMultiCalc {

    static Double RESULT = null;

    /**
     * 匹配 + - * / ( ) 運算符
     */
    static final String SYMBOL = "\\+|-|\\*|/|\\(|\\)|%";
    static final String LEFT = "(";
    static final String RIGHT = ")";
    static final String ADD = "+";
    static final String MINUS = "-";
    static final String TIMES = "*";
    static final String DIVISION = "/";
    static final String MOD = "%";

    /**
     * 加減 + -
     */
    static final int LEVEL_01 = 1;
    /**
     * 乘除 * /
     */
    static final int LEVEL_02 = 2;

    /**
     * 括號
     */
    static final int LEVEL_HIGH = Integer.MAX_VALUE;


    static Stack<String> stack = new Stack<String>();
    static List<String> data = Collections.synchronizedList(new ArrayList<String>());

    /**
     * 去除所有空白符
     *
     * @param s
     * @return
     */
    public static String replaceAllBlank(String s) {
        // \\s+ 匹配任何空白字符，包括空格、製表符、換頁符等等, 等價於[ \f\n\r\t\v]
        return s.replaceAll("\\s+", "");
    }

    /**
     * 判斷是不是數字 int double long float
     *
     * @param s
     * @return
     */
    public static boolean isNumber(String s) {
        Pattern pattern = Pattern.compile("^[-\\+]?[.\\d]*$");
        return pattern.matcher(s).matches();
    }

    /**
     * 判斷是不是運算符
     *
     * @param s
     * @return
     */
    public static boolean isSymbol(String s) {
        return s.matches(SYMBOL);
    }

    /**
     * 匹配運算等級
     *
     * @param s
     * @return
     */
    public static int calcLevel(String s) {
        if ("+".equals(s) || "-".equals(s)) {
            return LEVEL_01;
        } else if ("*".equals(s) || "/".equals(s) || "%".equals(s)) {
            return LEVEL_02;
        }
        return LEVEL_HIGH;
    }

    /**
     * 匹配
     *
     * @param s
     * @throws Exception
     */
    public static List<String> doMatch(String s) throws Exception {
        if (s == null || "".equals(s.trim())) throw new RuntimeException("data is empty");
        if (!isNumber(s.charAt(0) + "")) throw new RuntimeException("data illeagle,start not with a number");
        s = replaceAllBlank(s);
        String each;
        int start = 0;
        for (int i = 0; i < s.length(); i++) {
            if (isSymbol(s.charAt(i) + "")) {
                each = s.charAt(i) + "";
                //棧爲空，(操作符，或者 操作符優先級大於棧頂優先級 && 操作符優先級不是( )的優先級 及是 ) 不能直接入棧
                if (stack.isEmpty() || LEFT.equals(each)
                        || ((calcLevel(each) > calcLevel(stack.peek())) && calcLevel(each) < LEVEL_HIGH)) {
                    stack.push(each);
                } else if (!stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek())) {
                    //棧非空，操作符優先級小於等於棧頂優先級時出棧入列，直到棧爲空，或者遇到了(，最後操作符入棧
                    while (!stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek())) {
                        if (calcLevel(stack.peek()) == LEVEL_HIGH) {
                            break;
                        }
                        data.add(stack.pop());
                    }
                    stack.push(each);
                } else if (RIGHT.equals(each)) {
                    // ) 操作符，依次出棧入列直到空棧或者遇到了第一個)操作符，此時)出棧
                    while (!stack.isEmpty() && LEVEL_HIGH >= calcLevel(stack.peek())) {
                        if (LEVEL_HIGH == calcLevel(stack.peek())) {
                            stack.pop();
                            break;
                        }
                        data.add(stack.pop());
                    }
                }
                start = i;    //前一個運算符的位置
            } else if (i == s.length() - 1 || isSymbol(s.charAt(i + 1) + "")) {
                each = start == 0 ? s.substring(start, i + 1) : s.substring(start + 1, i + 1);
                if (isNumber(each)) {
                    data.add(each);
                    continue;
                }
                throw new RuntimeException("data not match number");
            }
        }
        //如果棧裏還有元素，此時元素需要依次出棧入列，可以想象棧裏剩下棧頂爲/，棧底爲+，應該依次出棧入列，可以直接翻轉整個stack 添加到隊列
        Collections.reverse(stack);
        data.addAll(new ArrayList<String>(stack));
        System.out.println(data);
        return data;
    }

    /**
     * 算出結果
     *
     * @param list
     * @return
     */
    public static Double doCalc(List<String> list) {
        //data.clear();
        Double d = 0d;
        if (list == null || list.isEmpty()) {
            return null;
        }
        if (list.size() == 1) {
            System.out.println(list);
            d = Double.valueOf(list.get(0));
            RESULT = d;
            return d;
        }
        ArrayList<String> list1 = new ArrayList<String>();
        for (int i = 0; i < list.size(); i++) {
            list1.add(list.get(i));
            if (isSymbol(list.get(i))) {
                Double d1 = doTheMath(list.get(i - 2), list.get(i - 1), list.get(i));
                list1.remove(i);
                list1.remove(i - 1);
                list1.set(i - 2, d1 + "");
                list1.addAll(list.subList(i + 1, list.size()));
                break;
            }
        }
        doCalc(list1);
        stack.clear();
        data.clear();
        return d;
    }

    /**
     * 運算
     *
     * @param s1
     * @param s2
     * @param symbol
     * @return
     */
    public static Double doTheMath(String s1, String s2, String symbol) {
        Double result;
        switch (symbol) {
            case ADD:
                result = Double.valueOf(s1) + Double.valueOf(s2);
                break;
            case MINUS:
                result = Double.valueOf(s1) - Double.valueOf(s2);
                break;
            case TIMES:
                result = Double.valueOf(s1) * Double.valueOf(s2);
                break;
            case DIVISION:
                result = Double.valueOf(s1) / Double.valueOf(s2);
                break;
            case MOD:
                result = Double.valueOf(s1) % Double.valueOf(s2);
                break;
            default:
                result = null;
        }
        return result;

    }
}

使用方法：

       String s = "(3+2)*3%4";
       ReversePolishMultiCalc.doCalc( ReversePolishMultiCalc.doMatch( s ) );
       String result = String.valueOf( ReversePolishMultiCalc.RESULT );

例：
中綴表達式轉波蘭後綴式實現Android計算器