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Java Program to concatenate two string.

Java Code Example — String Programs

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Java Program to concatenate two string.

Objective

Write a Java program to concatenate (join) two strings together.

Algorithm / Approach

  1. Read the first string from the user and store it in s1.
  2. Read the second string from the user and store it in s2.
  3. Use the concat() method: s1.concat(s2) to join them.
  4. Store the returned result in a third string s3.
  5. Print the concatenated string.
Test.java 
import java.util.Scanner;
class Test {
 public static void main(String[] a)
 {
  Scanner s=new Scanner(System.in);
  System.out.print("Enter 1st String: ");
  String s1=s.nextLine();
  System.out.print("Enter 2nd String: ");
  String s2=s.nextLine();
  String s3=s1.concat(s2);
  System.out.print("Concat. String: "+s3);
 }
}

Expected Output

Enter 1st String: Java
Enter 2nd String: Prowess
Concat. String: JavaProwess

Explanation of the Program

  • Concatenation is the process of appending one string to the end of another.
  • Java provides multiple ways to concatenate strings. You can use the built-in concat() method as shown here, or simply use the + operator (e.g., s1 + s2).
  • Remember that strings are immutable. The concat() method doesn't change s1; instead, it creates and returns a brand new string containing the combined text.

Complexity

Time Complexity O(n + m) - Where n and m are the lengths of the two strings.
Space Complexity O(n + m) - To create the new concatenated string object.
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