What are concatenating strings in Java, and how do you use it?

String Concatenation in Java

In java, string concatenation forms a new string that is the combination of multiple strings. There are two ways to concat string in java:

1. By + (string concatenation) operator
2. By concat() method

1) String Concatenation by + (string concatenation) operator

Java string concatenation operator (+) is used to add strings. For Example:

class TestStringConcatenation1{

public static void main(String args[]){

String s="Sachin"+" Tendulkar";

System.out.println(s);//Sachin Tendulkar

}

}

Output:Sachin Tendulkar

The Java compiler transforms above code to this:

String s=(new StringBuilder()).append("Sachin").append(" Tendulkar).toString();

In java, String concatenation is implemented through the StringBuilder (or StringBuffer) class and its append method. String concatenation operator produces a new string by appending the second operand onto the end of the first operand. The string concatenation operator can concat not only string but primitive values also. For Example:

class TestStringConcatenation2{

public static void main(String args[]){

String s=50+30+"Sachin"+40+40;

System.out.println(s);//80Sachin4040

}

}

Output: 80Sachin4040

2) String Concatenation by concat() method

The String concat() method concatenates the specified string to the end of current string. Syntax:

public String concat(String another)

Let's see the example of String concat() method.

class TestStringConcatenation3{

public static void main(String args[]){

String s1="Sachin ";

String s2="Tendulkar";

String s3=s1.concat(s2);

System.out.println(s3);//Sachin Tendulkar

}

}

Output: Sachin Tendulkar