Count and print number of repeated word occurrences in a String in Java

In this article, we will count and print number of repeated word occurrences in a String i.e.;

From a given String, we will be counting & printing

  • Number of repeated words
  • Along with its count

 

Steps for counting repeated word occurrences:

  1. Create empty HashMap of type String & Integer
  2. Split the String using space a delimiter and assign it to String[]
  3. Iterate through String[] array after splitting using for-each loop
  4. Note: we will convert all strings into lowercase before checking for case-insensitive purpose
  5. Check whether particular word is already present in the HashMap using containsKey(k) method of Map interface
  6. If it contains, then increase the count value by 1 using put(K, V) method of Map
  7. Otherwise insert using put() method of Map with count value as 1
  8. Finally, print Map using keySet() or entrySet() method of Map.Entry interface
  9. Code sorting logic for printing count value in descending order using Comparator interface
  10. Again print after sorting

 

ReadCountPrintRepeatedWordOccurencesInString.java

package in.bench.resources.count.print.occurences;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class ReadCountPrintRepeatedWordOccurencesInString {

	// main() method - entry point to start execution
	public static void main(String[] args) {

		// sample test string
		String testStr = "Science blank Maths blank blank"
				+ " Physics blank Maths";

		// invoke to count & print for supplied file
		countAndPrintRepeatedWordOccurences(testStr);
	}

	/**
	 * this method is used 
	 * to count number repeated word occurrences
	 * @param fileName
	 */
	public static void countAndPrintRepeatedWordOccurences(
			String strContent) {

		// Step 1: create Map of String-Integer
		Map<String, Integer> mapOfRepeatedWord = 
				new HashMap<String, Integer>();

		// Step 2: split line using space as delimiter
		String[] words = strContent.split(" ");

		// Step 3: iterate through String[] array
		for(String word : words) {

			// Step 4: convert all String into lower case, 
			// before comparison
			String tempUCword = word.toLowerCase();

			// Step 5: check whether Map contains particular word 
			if(mapOfRepeatedWord.containsKey(tempUCword)){

				// Step 6: If contains, increase count value by 1
				mapOfRepeatedWord.put(tempUCword, 
						mapOfRepeatedWord.get(tempUCword) + 1);
			} 
			else {

				// Step 7: otherwise, make a new entry
				mapOfRepeatedWord.put(tempUCword, 1);
			}
		}

		System.out.println("Before sorting : \n");
		System.out.println("Words" + "\t\t" + "Count");
		System.out.println("======" + "\t\t" + "=====");

		// Step 8: print word along with its count
		for(Map.Entry<String, Integer> entry : 
			mapOfRepeatedWord.entrySet()){
			System.out.println(entry.getKey() 
					+ "\t\t" + entry.getValue());
		}

		// Step 9: Sorting logic by invoking sortByCountValue()
		Map<String, Integer> wordLHMap = sortByCountValue(
				mapOfRepeatedWord);

		System.out.println("\n\nAfter sorting"
				+ " in descending order of count : \n");
		System.out.println("Words" + "\t\t" + "Count");
		System.out.println("======" + "\t\t" + "=====");

		// Step 10: Again print after sorting
		for(Map.Entry<String, Integer> entry : 
			wordLHMap.entrySet()) {
			System.out.println(entry.getKey() 
					+ "\t\t" + entry.getValue());
		}
	}

	/**
	 * this method sort acc. to count value
	 * @param mapOfRepeatedWord
	 * @return
	 */
	public static Map<String, Integer> sortByCountValue(
			Map<String, Integer> mapOfRepeatedWord) {

		// get entrySet from HashMap object
		Set<Map.Entry<String, Integer>> setOfWordEntries = 
				mapOfRepeatedWord.entrySet();

		// convert HashMap to List of Map entries
		List<Map.Entry<String, Integer>> listOfwordEntry = 
				new ArrayList<Map.Entry<String, Integer>>(
						setOfWordEntries);

		// sort list of entries using Collections.sort(ls, cmptr);
		Collections.sort(listOfwordEntry, 
				new Comparator<Map.Entry<String, Integer>>() {

			@Override
			public int compare(Entry<String, Integer> es1, 
					Entry<String, Integer> es2) {
				return es2.getValue().compareTo(es1.getValue());
			}
		});

		// store into LinkedHashMap for maintaining insertion
		Map<String, Integer> wordLHMap = 
				new LinkedHashMap<String, Integer>();

		// iterating list and storing in LinkedHahsMap
		for(Map.Entry<String, Integer> map : listOfwordEntry){
			wordLHMap.put(map.getKey(), map.getValue());
		}

		return wordLHMap;
	}
}

Output:

Before sorting : 

Words		Count
======		=====
blank		4
maths		2
science		1
physics		1


After sorting in descending order of count : 

Words		Count
======		=====
blank		4
maths		2
science		1
physics		1

Note: Stop at Step 8, if there is no business requirements for sorting either way (ascending or descending)

 

Reading from file in Java 1.7 version:

  • In the above example, we counted repeated words from String content
  • Similarly, we can read file from local drive location and count number of repeated words
  • While doing so, we need to provide catch block with FileNotFoundException and IOException for exception raised, as we are dealing with files
  • we will use try-with-resources statement introduced in Java 1.7 version, as it handles automatic resource management implicitly i.e.;
  • auto-closing of opened resources without explicit closing inside finally block after necessary null-safety checks
  • thus, it improves readability of the code by reducing number of lines of code

 

Sample text file:

ReadingFromFileInJava7.java

package in.bench.resources.count.print.occurences;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;

public class ReadPrintCharFromFileInJava7 {

	public static void main(String[] args) {

		// invoke to count & print for supplied file
		countAndPrintRepeatedCharacterOccurences("D://WORKSPACE/"
				+ "TEST_WORKSPACE/Java_8_Project/BRN2.txt");
	}

	/**
	 * this method is used
	 * to count number repeated word occurrences
	 * @param fileName
	 */
	public static void countAndPrintRepeatedCharacterOccurences(
			String fileName) {

		// local variables
		String line = "";

		// Step 1: create Map of Character-Integer
		Map<Character, Integer> mapOfRepeatedChar = 
				new HashMap<Character, Integer>();

		// Step A: Read file using try-with-resources statement
		try(BufferedReader bufferedReader = new BufferedReader(
				new FileReader(fileName))) {

			// Step B: Read line from file
			while ((line = bufferedReader.readLine()) != null) {

				// Step 2: convert String into character-array
				// using toCharArray() method 
				char[] chArray = line.toCharArray();

				// Step 3: iterate through char[] array
				for(char ch : chArray) {

					// Step 4: leave spaces
					if(ch != ' '){

						// Step 5: check 
						// whether Map contains same character
						if(mapOfRepeatedChar.containsKey(ch)){

							// Step 6: If contains, 
							// increase count value by 1
							mapOfRepeatedChar.put(ch, 
								   mapOfRepeatedChar.get(ch) + 1);
						} 
						else {

							// Step 7: otherwise, make a new entry
							mapOfRepeatedChar.put(ch, 1);
						}
					}
				}
			}

			System.out.println("Before sorting : \n");
			System.out.println("Char" + "\t" + "Count");
			System.out.println("====" + "\t" + "=====");

			// Step 8: get keySet() for iteration 
			Set<Character> character = mapOfRepeatedChar.keySet();

			// Step 9: print word along with its count
			for(Character ch : character) {
				System.out.println(ch 
						+ "\t" + mapOfRepeatedChar.get(ch));
			}

			// Step 10: Sorting logic
			// by invoking sortByCountValue()
			Map<Character, Integer> wordLHMap = sortByCountValue(
					mapOfRepeatedChar);

			System.out.println("\n\nAfter sorting"
					+ " in descending order of count : \n");
			System.out.println("Char" + "\t" + "Count");
			System.out.println("====" + "\t" + "=====");

			// Step 11: Again print after sorting
			for(Map.Entry<Character, Integer> entry : 
				wordLHMap.entrySet()){
				System.out.println(entry.getKey() 
						+ "\t" + entry.getValue());
			}
		}
		catch (FileNotFoundException fnfex) {
			fnfex.printStackTrace();
		}
		catch (IOException ioex) {
			ioex.printStackTrace();
		}
	}

	/**
	 * this method sort acc. to count value
	 * @param mapOfRepeatedWord
	 * @return
	 */
	public static Map<Character, Integer> sortByCountValue(
			Map<Character, Integer> mapOfRepeatedWord) {

		// get entrySet from HashMap object
		Set<Map.Entry<Character, Integer>> setOfWordEntries = 
				mapOfRepeatedWord.entrySet();

		// convert HashMap to List of Map entries
		List<Map.Entry<Character, Integer>> listOfwordEntry = 
				new ArrayList<Map.Entry<Character, Integer>>(
						setOfWordEntries);

		// sort list of entries using Collections.sort(ls, cmptr);
		Collections.sort(listOfwordEntry, 
				new Comparator<Map.Entry<Character, Integer>>() {

			@Override
			public int compare(Entry<Character, Integer> es1, 
					Entry<Character, Integer> es2) {
				return es2.getValue().compareTo(es1.getValue());
			}
		});

		// store into LinkedHashMap for maintaining insertion
		Map<Character, Integer> wordLHMap = 
				new LinkedHashMap<Character, Integer>();

		// iterating list and storing in LinkedHahsMap
		for(Map.Entry<Character, Integer> map : listOfwordEntry) {
			wordLHMap.put(map.getKey(), map.getValue());
		}

		return wordLHMap;
	}
}

Output:

Before sorting : 

Words		Count
======		=====
MATHS		2
BLANK		4
SCIENCE		1
PHYSICS		1


After sorting in descending order of count : 

Words		Count
======		=====
BLANK		4
MATHS		2
SCIENCE		1
PHYSICS		1

Note: Stop at Step 8, if there is no business requirements for sorting either way (ascending or descending)

 

Hope, you found this article very helpful. If you any suggestion or want to contribute to improve this article, then share with us. We will include that code here.

 

Happy Coding !!
Happy Learning !!

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