String Concatenation Example in Java

Introduction

String Concatenation is a classic Java console program that demonstrates the concept with complete source code and sample output. Strings are immutable objects in Java; the examples show comparison, searching and transformation.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

A string is traditionally a sequence of characters, either as a literal constant or as some kind of variable. The latter may allow its elements to be mutated and the length changed, or it may be fixed (after creation). A string is generally understood as a data type and is often implemented as an array of bytes (or words) that stores a sequence of elements. A string may also denote more general arrays or other sequence (or list) data types and structures.

Syntax

Variable_name=Variable_name1.concat(Variable_name2);

String Concatenation Example Program

import java.util.Scanner;

public class StringConcatenation{
	public static void main(String[] args){
	String result;
	Scanner in=new Scanner(System.in);
	System.out.println("Enter the string1: ");
	String str1=in.nextLine();
	System.out.println("Enter the string2: ");
	String str2=in.nextLine();
	result=str1.concat(str2);
    System.out.println("The resulting string is: "+result);
	}
}

Sample Output

Enter the string1:
she
Enter the string2:
eats
The resulting string is: she eats

When to use

Use string manipulation when cleaning user input, parsing text files or formatting messages.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.util.Scanner; imports a class used later in the program.

3. A Scanner reads typed input from the keyboard (System.in).

4. A println / print call writes text to the console — part of the sample output below.

5. String str1=in.nextLine(); updates a variable used in the calculation or output.

6. A println / print call writes text to the console — part of the sample output below.

7. String str2=in.nextLine(); updates a variable used in the calculation or output.

8. A println / print call writes text to the console — part of the sample output below.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.