Knuth-Morris-Pratt Algorithm.

public class StringMatcherAlgorithm {

    /**
     * indicates the largest possible shift S if mismatching the pattern.
     * @param pattern  the pattern you want to search for in above text,like a word.
     * @return the length of the longest prefix of P that is a suffix of P[i . . j].
     * 
     */
    //text:         a b a c a a b a c c
    //pattern:  a b a c a b
    static int[] failure(char[] pattern){
        //length of the previous longest prefix suffix
        int m = pattern.length;
        int[] f = new int[m]; 
        int i = 1;
        int j = 0;
        f[0] = 0;
        while(i < m){
            if(pattern[i] == pattern[j]){
                f[i] = j+1;
                i = i+1;
                j = j+1;
            }else if(j > 0){
                j = f[j-1];
            }else{
                f[i] = 0;
                i = i+1;
            }
        }
        return f;
    }
    /**
     * Knuth-Morris-Pratt algorithm.
     * @param text the text such as a sentence,an article and so on.
     * @param pattern the pattern you want to search for in above text,like a word.
     * @return the index of the pattern in the text if match the pattern
     */
    public static List<Integer> KMP(char[] text, char[] pattern){
        int[] f = failure(pattern);
        int n = text.length;
        int m = pattern.length;
        List<Integer> list = new ArrayList<Integer>();
        int i = 0;
        int j = 0;
        while(i < n){
            if(text[i] == pattern[j]){
                i = i+1;
                j = j+1;
            }
            if(j == m){//find pattern
                list.add(i-j);
                j = f[j-1];//the pattern slide to the next window
            }
            else if(i < n && text[i] != pattern[j]){
                if(j != 0)
                    j = f[j-1];
                else//j == 0 indicate the first character of the pattern mismatch the character ,text[i]
                    i = i+1;
            }
        }
        return list;
    }
}

Reference:
http://www.personal.kent.edu/~rmuhamma/Algorithms/MyAlgorithms/StringMatch/kuthMP.htm

https://www.geeksforgeeks.org/searching-for-patterns-set-2-kmp-algorithm/

http://jakeboxer.com/blog/2009/12/13/the-knuth-morris-pratt-algorithm-in-my-own-words/
http://www.iti.fh-flensburg.de/lang/algorithmen/pattern/kmpen.htm