Java 문자열을 산술 표현식으로 변환하여 결과를 계산하고 출력하는 코드

package cn.anycall.test;  
  
import java.math.BigDecimal;  
  
public class TestSHU {  
  
    public static String addBigDecimal(String a, String b) {     
        double a1 = Double.parseDouble(a);     
        double b1 = Double.parseDouble(b);     
        BigDecimal a2 = BigDecimal.valueOf(a1);     
        BigDecimal b2 = BigDecimal.valueOf(b1);     
        BigDecimal c2 = a2.add(b2);     
        String c1 = c2 + "";     
        return c1;     
    }    
    public static String reduceBigDecimal(String a, String b) {     
        double a1 = Double.parseDouble(a);     
        double b1 = Double.parseDouble(b);     
        BigDecimal a2 = BigDecimal.valueOf(a1);     
        BigDecimal b2 = BigDecimal.valueOf(b1);     
        BigDecimal c2 = a2.subtract(b2);     
        String c1 = c2 + "";     
        return c1;     
    }    
    public static String multipliedString(String a, String b) {     
        double a1 = Double.parseDouble(a);     
        double b1 = Double.parseDouble(b);     
        BigDecimal a2 = BigDecimal.valueOf(a1);     
        BigDecimal b2 = BigDecimal.valueOf(b1);     
        BigDecimal c2 = a2.multiply(b2);     
        String c1 = c2 + "";     
        return c1;     
    }    
    public static String divideString(String a, String b) {     
        double a1 = Double.parseDouble(a);     
        double b1 = Double.parseDouble(b);     
        BigDecimal a2 = BigDecimal.valueOf(a1);     
        BigDecimal b2 = BigDecimal.valueOf(b1);     
        BigDecimal c2 = a2.divide(b2,a2.scale());     
        String c1 = c2 + "";     
        return c1;     
    }    
  
    public static String yunsuanjibie(String s) {  
        String r = "";  
        int p = 0;  
        for (int i = 0; i < s.length(); i++) {  
                    || s.charAt(i) == '/') {  
                p++;  
            }  
        }  
        int k1 = 0;  
        int first = 0;  
        for (int i = 0; i < s.length(); i++) {  
                    || s.charAt(i) == '/') {  
                k[k1] = s.substring(first, i);  
                k1++;  
                k[k1] = "" + s.charAt(i);  
                k1++;  
                first = i + 1;  
            }  
        }  
        k[k1] = s.substring(first, s.length());  
        int kp = p;  
        while (kp > 0) {  
            for (int i = 0; i < k.length; i++) {  
                    int l;  
                    for (l = i - 1; l > -1; l--) {  
                        if (!(k[l].equals("p")))  
                            break;  
                    }  
                    int q;  
                    for (q = i + 1; q < k.length; q++) {  
                        if (!(k[l].equals("p")))  
                            break;  
                    }  
                        k[i] = ""+ multipliedString(k[l],k[q]);  
                        k[l] = "p";  
                        k[q] = "p";  
                        kp--;  
                    } else {  
                        k[i] = ""+divideString(k[l],k[q]);  
                        k[l] = "p";  
                        k[q] = "p";  
                        kp--;  
                    }  
                    break;  
                }  
            }  
                if (k[i].equals("+") || k[i].equals("-")) {  
                    int l;  
                    for (l = i - 1; l > -1; l--) {  
                        if (!(k[l].equals("p")))  
                            break;  
                    }  
                    int q;  
                    for (q = i + 1; q < k.length; q++) {  
                        if (!(k[q].equals("p")))  
                            break;  
                    }  
                    if (k[i].equals("+")) {  
                        k[i] = ""+addBigDecimal(k[l],k[q]);  
                        k[l] = "p";  
                        k[q] = "p";  
                        kp--;  
                    } else {  
                        k[i] = ""+reduceBigDecimal(k[l],k[q]);  
                        k[l] = "p";  
                        k[q] = "p";  
                        kp--;  
                    }  
                    break;  
                }  
            }  
            for (int i = 0; i < k.length; i++) {  
                if (!(k[i].equals("p"))) {  
                    r = k[i];  
                    break;  
                }  
            }  
        }  
        return r;  
    }  
  
    public static void sizeyunsuan(String s) {  
        while (true) {  
            int first = 0;  
            int last = 0;  
            for (int i = 0; i < s.length(); i++) {  
                if (s.charAt(i) == '(')  
                    first = i;  
                if (s.charAt(i) == ')') {  
                    last = i;  
                    break;  
                }  
            }  
            if (last == 0) {  
                System.out.println(yunsuanjibie(s));  
                return;  
            } else {  
                String s1 = s.substring(0, first);  
                String s2 = s.substring(first + 1, last);  
                String s3 = s.substring(last + 1, s.length());  
                s = s1 + yunsuanjibie(s2) + s3;  
            }  
        }  
    }  
  
    public static void main(String[] args) {  
        sizeyunsuan(s);  
    }  
  
}