String someString = "elephant";

long count = someString.chars().filter(ch -> ch == 'e').count();

assertEquals(2, count);

long count2 = someString.codePoints().filter(ch -> ch == 'e').count();

assertEquals(2, count2);

​

package com.javaguides.strings.examples;

​

/**

 * 

 * Java program to count number of occurrence of substring in given string.

 * @author javaguides.net

 * 

 */

public class CountOccuranceOfSubString {

​

    public static void main(String[] args) {

        int count = countOccurrencesOf("javadevelopersguides", "java");

        System.out.println("Count number of occurrences of substring 'java' " +

            " in string 'javadevelopersguides' : " + count);

        int count1 = countOccurrencesOf("javajavaguides", "java");

        System.out.println("Count number of occurrences of substring 'java'" +

            "  in string 'javajavaguides' : " + count1);

    }

​

    public static boolean hasLength(String str) {

        return (str != null && !str.isEmpty());

    }

​

    /**

     * Count the occurrences of the substring {@code sub} in string {@code str}.

     * @param str string to search in

     * @param sub string to search for

     */

    public static int countOccurrencesOf(String str, String sub) {

        if (!hasLength(str) || !hasLength(sub)) {

            return 0;

        }

​

        int count = 0;

        int pos = 0;

        int idx;

        while ((idx = str.indexOf(sub, pos)) != -1) {

            ++count;

            pos = idx + sub.length();

        }

        return count;

    }

}

String line = "apples.oranges.bananas";

int count = line.length() - line.replace(".", "").length();

System.out.println(count);//displays 2

main(){

    String[] array ={"a","ab","a","abc","abc","a","ab","ab","a"};

    Map<String,Integer> hm = new HashMap();

​

    for(String x:array){

​

        if(!hm.containsKey(x)){

            hm.put(x,1);

        }else{

            hm.put(x, hm.get(x)+1);

        }

    }

    System.out.println(hm);

}

public class SubstringOccurrenceCounter {

    public static int countOccurrences(String string, String substring) {

        int count = 0;

        int index = 0;

​

        while (index != -1) {

            index = string.indexOf(substring, index);

            if (index != -1) {

                count++;

                index += substring.length();

            }

        }

​

        return count;

    }

​

    public static void main(String[] args) {

        String string = "Java is awesome and Java is powerful";

        String substring = "Java";

        int occurrenceCount = countOccurrences(string, substring);

​

        System.out.println("Number of occurrences: " + occurrenceCount);

    }

}