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Java String concat() Method with Examples

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The concatenation function in Java makes a new string composed of multiple strings. There are two ways of combining strings in Java: The +string operator is used. Use the concat() method.

String Concatenation by + (String concatenation) operator

The Java string concatenation function is used to insert strings.

Example:

classTechvidvan{  
public static void main(String args[]){  
String s="Sachin"+" Tendulkar";  
System.out.println(s);
 }  
}

Output:
Sachin Tendulkar

Concatenation of strings using the concat() method

The string concat() method concatenates a given string to the end of an existing string.

Syntax: public String concatString other

How to concatenate strings in Java

  • Concatenation is combining two or more strings to form a new string by appending the next string to the end of the previous strings.
  • In Java, two strings can be concatenated using the + or += operator or the concat() method, defined in the java.lang.string class.
  • This shot will discuss how to perform string concatenation using both methods.

Example:

The program below demonstrates how to concatenate two strings using the + operator in Java.

class Techvidvan{
public static void main( String args[] )
{ 
String first = "Hello";
String second = "World"; 
String third = first + second; 
System.out.println(third); 
// yet another way to concatenate strings 
first += second;
 System.out.println(first);
 }

Output:
HelloWorld
HelloWorld

Parameter:

stringToConcat is the string to be concatenated. It will be appended at the end of the string object calling this method.

Return type:

The concat() method returns the concatenated string.

String concatenation using StringBuilder class

  • To perform concatenation operations, StringBuilder is a class that provides an append() method.
  • Arguments of other types, such as objects, string builders, int, char, CharSequence, boolean, float, and double, are accepted by the append() method.
  • The most popular and fastest way to concatenate strings in Java is StringBuilder.
  • It is an immutable class, which means you can update or change the values ​​in the StringBuilder object.

Example:

public class Techvidvan
{   
public static void main(String args[])  
{  
StringBuilder s1 = new StringBuilder("Hello");    
StringBuilder s2 = new StringBuilder(" World");   
StringBuilder s = s1.append(s2);  
System.out.println(s.toString());   
}  
}

Output:
Hello World

s1, s2 and s are defined as StringBuilder objects by the code snippet above. Using an append method, S will store the result by concatenating s1 and s2.

Concatenation of strings using the format() method

The String.format() method can combine multiple strings with a format specification such as %s followed by string values or objects.

Example:

public class Techvidvan
{  
public static void main(String args[])  
{  
String s1 = new String("Hello");      
String s2 = new String(" World");      
String s = String.format("%s%s",s1,s2);
System.out.println(s.toString());   
}  
}

Output:
Hello World

Here, the String s objects are assigned the concatenated result of the strings s1 and s2 using the String.format() method. format() accepts parameters as a format specifier followed by objects or String values.

Concatenate strings using the String.join() method (Java version 8+)

The String.join() method is available in Java version 8 and all versions above. The String.join() method accepts arguments, first a delimiter and an array of String objects.

Example:

public class Techvidvan{ 
    public static void main(String args[])  
    {  
        String s1 = new String("Hello");      
        String s2 = new String(" World");   
        String s = String.join("",s1,s2);   
        System.out.println(s.toString());   
    }  
}

Output:
Hello World

The result of the String.join “”,s1,s2″ method will be stored by a string object s in this code snippet. The delimiter is enclosed in a quotation mark next to the string object or array of string objects.

String concatenation using StringJoiner class (Java Version 8+)

StringJoiner class has all the functionalities of String.join() method. In advance, its constructor can also accept optional arguments, prefixes and suffixes.

Example:

public class Techvidvan{   
    public static void main(String args[])  
    {  
        StringJoiner s = new StringJoiner(", ");    
        s.add("Hello");     
        s.add("World");    
        System.out.println(s.toString());  
    }  
}

Output:
Hello, World

A StringJoiner item s is declared in this code snippet, and the stringjoiner constructor takes a separator value. Inside the quotation marks, a separator is indicated. The add() method will append the Strings passed as arguments.

String concatenation using the Collectors.joining (JavaVersion 8+)

The join() function of the Collectors class in Java 8 provides input elements to be grouped into a similar order as they are.

Example:

import java.util.*;  
import java.util.stream.Collectors;  
public class Techvidvan 
{  
     public static void main(String args[])  
    {  
        List<String> liststr = Arrays.asList("abc", "pqr", "xyz");
       String str = liststr.stream().collect(Collectors.joining(", "));                   System.out.println(str.toString());    
    }  
}

Output:

abc, pqr, xyz

You have a list of string fields. The result of the Collectors.joining() method is held in a String object.

Conclusion

A brief description of Java string concatenation is provided in this article. We’ve also discussed using concat() and “+” operators for strings. We’ve also compared the concat() method and the “+” operator and how to choose one to use in different contexts.

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