Brute force matching of Java pattern matching

Brute force matching of Java pattern matching

package javay.util;
 

public class PMBF {
 
  
  public static int patternMatch(String target, String pattern) {
    int targetLength = target.length();
    int patternLength = pattern.length();
    int idxTgt = 0; //The position of a character in the target string
    int idxPtn = 0; //The position of characters in a pattern string
 
    int index = 0; //Saves the position of the starting character that matches ing to the pattern string
    while(idxTgt < targetLength && idxPtn < patternLength) {
      //Find a matching character
      if(target.charAt(idxTgt) == pattern.charAt(idxPtn)) {
        //If they are equal, a subsequent comparison of the characters continues
        idxTgt ++;
        idxPtn ++;
      } else {
        //Otherwise the target string starts from the second character and is recompared to the first character of the pattern string
        index ++;
        idxPtn = 0;
        idxTgt = index;
      }
    }
    //Match to one, output the result
    if(idxPtn == patternLength) {
      //Indicating a successful match
      return index;
    } else {
      return -1;
    }
  }
}

Examples of use:

static int indexOf(char[] source,char[] target) {
    char first = target[0];
    int max = (source.length - target.length);
    for (int i = 0; i <= max; i++) {
      
      if (source[i] != first) {
        while (++i <= max && source[i] != first);
      }
      
      if (i <= max) {
        int j = i + 1;
        int end = j + target.length - 1;
        for (int k = 1; j < end && source[j] == target[k]; j++, k++);
        if (j == end) {
          
          return i ;
        }
      }
    }
    return -1;
  }

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