Java Program to Count Occurrences of Words in a String

Introduction

Counting the occurrences of words in a string is a common task in text processing. This exercise helps you understand how to manipulate strings and use data structures like maps in Java to store and count occurrences. This guide will walk you through writing a Java program that counts the occurrences of each word in a given string.

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Problem Statement

Create a Java program that:

• Prompts the user to enter a string.
• Splits the string into words.
• Counts the occurrences of each word in the string.
• Displays each word along with its count.

Example:

• Input: "Java is a programming language and Java is also an island"
• Output: Java: 2 is: 2 a: 1 programming: 1 language: 1 and: 1 also: 1 an: 1 island: 1

Solution Steps

1. Read the String: Use the Scanner class to take the string as input from the user.
2. Split the String into Words: Use the split() method to break the string into words.
3. Store Word Counts: Use a HashMap to store each word of the string as keys and their counts as values.
4. Display the Word Counts: Print each word along with its count.
5. Close Resources: Close the Scanner class object automatically using the try-resource statement.

Java Program

// Java Program to Count Occurrences of Words in a String

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class WordOccurrenceCounter {
    public static void main(String[] args) {
        // Step 1: Read the string from the user
        try (Scanner scanner = new Scanner(System.in)) {
            System.out.print("Enter a string: ");
            String input = scanner.nextLine();
            
            // Step 2: Split the string into words
            String[] words = input.split("\\s+");
            
            // Step 3: Store word counts
            Map<String, Integer> wordCountMap = new HashMap<>();
            for (String word : words) {
                word = word.toLowerCase();  // Normalize to handle case-insensitivity
                wordCountMap.put(word, wordCountMap.getOrDefault(word, 0) + 1);
            }
            
            // Step 4: Display the word counts
            System.out.println("Word occurrences:");
            for (Map.Entry<String, Integer> entry : wordCountMap.entrySet()) {
                System.out.println(entry.getKey() + ": " + entry.getValue());
            }
        }
    }
}

Explanation

Step 1: Read the String

• The Scanner class is used to read a string input from the user. The nextLine() method captures the entire line as a string.

Step 2: Split the String into Words

• The split() method is used to divide the string into words based on whitespace. The regex \\s+ handles multiple spaces between words.

Step 3: Store Word Counts

• A HashMap is used to store the words as keys and their counts as values. The words are converted to lowercase to handle case-insensitivity.

Step 4: Display the Word Counts

• The program iterates through the HashMap entries and prints each word along with its count.

Output

Enter a string: Java is a programming language and Java is also an island
Word occurrences:
java: 2
is: 2
a: 1
programming: 1
language: 1
and: 1
also: 1
an: 1
island: 1

Conclusion

This Java program demonstrates how to count and display the occurrences of words in a user-input string. It covers important concepts such as string manipulation, using maps to store word counts, and iterating through collections, making it a valuable exercise for beginners learning Java programming.

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