To implement Java Programs using Strings

Explanation

This Java program is designed to read a line of text (a string) from the user and then accurately count the number of words present in that string. It handles common issues like leading/trailing spaces and empty inputs.

Here's a step-by-step breakdown of its logic:

1. Import Scanner: The program begins by importing the java.util.Scanner class, which is essential for reading user input from the console.
2. Create Scanner Object: Inside the main method, an object of the Scanner class is created, linked to System.in (the standard input stream), allowing the program to receive input.
3. Prompt User: The program then displays a message "Enter a string: " to guide the user to input text.
4. Read Input: It reads the entire line of text entered by the user, including spaces, until the user presses Enter, and stores it in a String variable named input.
5. Trim Spaces: Crucially, the input.trim() method is called. This method removes any leading (beginning) and trailing (ending) whitespace characters (spaces, tabs, newlines) from the input string. This is important because leading/trailing spaces should not be counted as part of a word or affect the word count.
6. Handle Empty String: After trimming, the program checks if the input string is empty using input.isEmpty(). If the string is empty (meaning the user entered nothing, or only spaces which were then trimmed), it directly prints "Number of words: 0". This is an important edge case handling.
7. Split into Words: If the string is not empty, the core logic for counting words is executed. input.split(" ") is called. This method breaks the string into an array of substrings wherever a space (" ") is encountered. Each resulting substring is considered a word. For example, "Hello World" would become an array {"Hello", "World"}.
8. Count and Display: The words.length property gives the total number of elements in the words array, which directly corresponds to the number of words found. This count is then printed to the console.
9. Close Scanner: Finally, sc.close() is called to release the resources associated with the Scanner object, which is good practice.

Algorithm

The algorithm used to count words in the given string can be described as follows:

1. Start.
2. Initialize Input Mechanism: Create a Scanner object to read input from the console.
3. Prompt for Input: Display a message asking the user to enter a string.
4. Read String: Read the entire line of text entered by the user and store it in a String variable.
5. Clean String: Remove any leading or trailing whitespace characters from the input string using the trim() method.
6. Check for Empty String:
   • If the cleaned string is empty (after trimming), set the word count to 0.
   • Else (if the string is not empty):
     • Split String: Divide the string into an array of substrings (words) using a single space (" ") as the delimiter.
     • Count Words: The number of elements in this resulting array is the word count.
7. Display Result: Print the calculated word count to the console.
8. Close Resources: Close the Scanner object.
9. End.