String Concatenation in Java

String concatenation is an operation to concatenate two or more strings. In Java, we can concatenate strings using the different approaches. The following are some of the approaches to concatenate the strings:

• Using + operator

• Using string concat() method

• Using stringBuilder or stringBuffer class

String concatenation using + operator

The + operator is a simple way to concatenate two strings It performs the concatenation operation directly between two operands (strings). This is a common method used due to its simplicity.

Example

Following example shows string concatenation by using "+" operator method

public class ConncatSample {
	public static void main(String []args) {
		String s1 = "Hello";
		String s2 = "world";
		String res = s1 + s2;
		System.out.print("Concatenation result:: ");
		System.out.println(res);
	}
}

output

Concatenation result:: Helloworld

String concatenation using concat() method

The string concat() method joins one string to the end of another string. It combines the two strings and returns the result. If any of the strings is null, it throws a NullPointerException.

Example

Following example shows concatenation string using concat() method

public class HelloWorld { 
   public static void main(String []args) {
      String s = "Hello"; 
      s = s.concat("world");
      System.out.print(s);
   }
}

output

Helloword

Using stringBuilder or stringBuffer class

The class StringBuilder provides append() method for performing concatenation operation, It takes various types of input arguments, that is Objects, StringBuilder, int, char, CharSequence, boolean, float, double. stringbuilder is the fastest and most popular way of concatenating strings in java.

Example

Following example shows concatenation of strings using stringBuilder or stringBuffer class

public class StringBuilderExample {  
    public static void main(String[] args) {  
        String firstName = "Mark";  
        String lastName = "Smith";  
        // Using StringBuilder for efficient string concatenation  
        StringBuilder sb = new StringBuilder();  
        sb.append("Hello, ");  
        sb.append(firstName);  
        sb.append(" ");  
        sb.append(lastName);  
        String result = sb.toString();  
        System.out.println(result);    
    }  
}  

output

Hello, Mark Smith