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Java Program to reverse a string "WORD BY WORD".

Java Code Example — String Programs

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Java Program to reverse a string "WORD BY WORD".

Objective

Write a Java program to reverse every individual word within a string while keeping their original sentence positions.

Algorithm / Approach

  1. Read a sentence from the user.
  2. Split the sentence into an array of words using split(" ").
  3. Initialize an empty accumulator string s2 = "".
  4. Loop through the array of words.
  5. Pass each individual word to the reverse() method.
  6. Append the reversed word and a space to s2.
  7. Print the final sentence.
Test.java 
import java.util.Scanner;
class Test {
 public String reverse(String x) {
  String rev = "";
  for(int i=x.length()-1; i>=0;i--) {
   rev = rev + x.charAt(i);
  }
  return rev;
 }
 public static void main(String[] a)
 {
  Test t = new Test();
  Scanner s=new Scanner(System.in);
  System.out.print("Enter String: ");
  String s1 = s.nextLine();
  String[] x = s1.split(" ");
  String s2="";
  for(int i=0; i< x.length; i++) {
   s2 =s2+ t.reverse(x[i])+" ";
  }
  System.out.print("Reverse = "+s2);
 }
}

Expected Output

Enter String: Java Prowess App
Reverse = avaJ sseworP ppA

Explanation of the Program

  • This program tackles a common interview question: reversing the characters of each word without reversing the order of the words themselves.
  • The split(" ") method is incredibly powerful. It breaks the single long sentence string into an array of individual word strings, using the space character as the delimiter.
  • Once we have an array of individual words, we simply run our standard reverse loop on each one and glue them back together.

Complexity

Time Complexity O(n) - Where n is the total number of characters in the sentence.
Space Complexity O(n)
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