如何检查字符串是否包含Java中的某些字符？

Question

I want to check for instance if string "ABCD" contains "DC" string in it in Java. But this is not a substring example, because every time my string and checking characters will change. and I store checking characters into an array, So substring failed, it only works if I have CD, or BC. and I couldn't do match since every time I call checking character from an array. SO what should I do any suggestion

Answer 1

I use this method for char and byte array. After you got the index of the src array where the sub is matched with, you then can store it anywhere you want. Try this:

public static int indexOf(char[] src, char[] sub) {
    int limit = src.length - sub.length;
    int i, j;
    for(i = 0; i < limit +1; ++i) {
        for(j = 0; j < sub.length; ++j) {
           if (src[i+j] != sub[j]) {
               break;
           }
        }
        if (j == sub.length)
               return i;
     }
   return -1;  
} 

Answer 2

here's some pseudocode to get you started

we'll call "ABCD" the source string and "DC" the target string

change source string to list of chars

change target string to list of chars

for each char in target list of char

    if source list does not contain target char
        return false;

return true

Answer 3

Get all the permutation of the source string till it contains the desired sub string

Permutation Logic based on

public static void main(String[] args) {
    System.out.println(Test.checkIfContains("ABCD", "DC"));
}

public static Boolean checkIfContains(String main, String check) {
    return permutation("", main, check);
}

private static Boolean permutation(String prefix, String main, String check) {
    int n = main.length();
    if (n == 0) {
        if (checkFor(prefix, check)) {
            return true;
        }
    } else {
        for (int i = 0; i < n; i++) {
            if (permutation(prefix + main.charAt(i), main.substring(0, i) + main.substring(i + 1, n), check)) {
                return true;
            }
        }
    }
    return false;
}

private static boolean checkFor(String prefix, String check) {
    return prefix.contains(check);
}

Answer 4

As I understand it, you want to see if all of the characters of the second string (which I called checkString) are contained in the first string (refString). I would proceed using a function like this

private boolean checkString(String refString, String checkString) {   
    boolean a;
    for (int i; i < checkString.length(); i++) {
        for (int j; j < refString.length(); j++) {
            a |= checkString.charAt(i) == refString.charAt(j);
        }
        if (!a) return false;
    }
    return true;
}

Which return true only when all the characters in checkString are in the reference string.