[Java知识库]java 求字符串形式bool表达式的值

分析字符串形式的布尔表达式，求取其对应的值

用字符‘T’代表true，字符‘F代表false，&? |? ！对应与或非

源码如下：

import java.util.ArrayList;
import java.util.List;


public class BoolString {
    private static void split(String value,List<Character> signs, List<String> parts) {
        int tier = 0;
        int start = 0;
        for (int i = 0; i < value.length(); i++) {
            char c = value.charAt(i);
            if (c == '(') {
                if (tier == 0) start = i + 1;
                tier++;
            }
            if (c == ')') {
                tier--;
                if (tier == 0) {
                    parts.add(value.substring(start, i));
                    start = i + 1;
                }
            }
            if (tier == 0) {
                if (c == '!') {
                    signs.add(c);
                    start++;
                }
                if (c == '&' || c == '|') {
                    signs.add(c);
                    if (start == i) {
                        start = i + 1;
                        continue;
                    }
                    parts.add(value.substring(start, i));
                    start += 2;
                }
            }
        }
        if (start < value.length()) parts.add(value.substring(start));
    }
    public static boolean parse(String the) {
        boolean root = false;
        List<Character> signs =new ArrayList<>();
        List<String> parts = new ArrayList<>();
        if (the.length() == 1) root = true;
        else {
            split(the,signs,parts);
        }
        if (!root) {
            boolean fast = parse(parts.get(0));
            boolean used = false;
            for (char c : signs) {
                if (c == '&' && !fast) {
                    used = true;
                    break;
                }
                if (c == '|' && fast) {
                    used = true;
                    break;
                }
            }
            if (used) {
                for (char c : signs) {
                    if (c == '!') {
                        fast = !fast;
                    } else return fast;
                }
            }
            int p = parts.size() - 1;
            boolean now = parse(parts.get(parts.size() - 1));
            for (int i = signs.size() - 1; i >= 0; i--) {
                if (p - 1 >= 0) {
                    Character sign = signs.get(i);
                    boolean b1 = parse(parts.get(p));
                    boolean b2 = parse(parts.get(p - 1));
                    while (true){
                        if (sign == '!') {
                            b1 = !b1;
                            if (i - 1 < 0) {
                                return b1;
                            }
                            i -= 1;
                            sign = signs.get(i);
                        }else break;
                    }
                    if (sign == '&') {
                        now = b1 && b2;
                        continue;
                    }
                    if (sign == '|') {
                        now = b1 || b2;
                        continue;
                    }
                }
                now = !now;
            }
            return now;
        } else return the.equals("T");
    }

}

转载须注明出处