without using built-in functions

Here is a java example that finds the occurrences of each string in every another string.

class  Occurrence
{
    public static void main(String[] args) 
    {
    String str = "all and sand falling wall and sand";
    String findStr = "and";
    int lastIndex = 0;
    int count = 0;

    while ((lastIndex = str.indexOf(findStr, lastIndex)) != -1) {
        count++;
        lastIndex += findStr.length() - 1;
    }

    System.out.println(findStr+" occurs " +count+ " times");

    }
}

Here is another code.

import java.util.*;

public class CountWordOccurrence {
        public static void main(String[] args){

        String[] st = {"all","and","sand","falling wall","and","sand"};
        HashMap<String, Integer> map = new HashMap<String, Integer>();
            String str="";
            for(int i=0;i<st.length;i++){
                str+=st[i]+" ";
            }
            str = str.toLowerCase(); 
                int count = -1;
                for (int i = 0; i < str.length(); i++) { 
                   if ((!Character.isLetter(str.charAt(i))) || (i + 1 == str.length())) { 
                            if (i - count > 1) { 
                            if (Character.isLetter(str.charAt(i))) 
                                i++;
                            String word = str.substring(count + 1, i);
                            if (map.containsKey(word)) { 
                            map.put(word, map.get(word) + 1);
                            }
                            else { 
                            map.put(word, 1);
                            } 
                        } 
                        count = i;
                    } 
                } 
        ArrayList<Integer> list = new ArrayList<Integer>();
        list.addAll(map.values());
        Collections.sort(list, Collections.reverseOrder());
        int last = -1;
        for (Integer i : list) { 
            if (last == i) 
                continue;
            last = i;
            for (String s : map.keySet()) { 
                if (map.get(s) == i) 
                    System.out.println(s + ":" + i);
            } 
        } 
    } 
}