# String concatenation in java

General meaning of concatenation means a series of interconnected things. String concatenation refers to the combination of more than one string.

## Ways of String concatenation:

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

## 1. By concatenation operator +:

String concatenation can be performed with + operator. String concatenation is performed by StringBuilder or StringBuffer class and its append method. Result will be a new string after appending second string at the end of the first string. Both string and primitive data type can be concatenated.
Compiler will transform it to:
String s=(new StringBuilder()).append(“firstString”).append(“secondString”).toString();

## Example:

StringConcatenationExample1.java

/** * This program is used to show the concatenation * of strings by + operator. * @author w3spoint */ class TestString{ String str1 = "www."; String str2 = "w3spoint."; String str3 = "com";   /** * This method is used to concatenate strings using + operator. * @author w3spoint */ public void concateStrings(){ System.out.println(str1 + str2 + str3); } }   public class StringConcatenationExample1 { public static void main(String args[]){ //creating TestString object. TestString obj = new TestString(); //method call obj.concateStrings(); } }

## Output:

www.w3spoint.com

Note: If any one of the two arguments of + operator is a string then result will be a string otherwise primitive type.

## Example:

StringConcatenationExample2.java

/** * This program is used to show the concatenation of * strings and primitive data types by + operator. * @author w3spoint. */ class TestString{ String str1 = "jai"; int num1 = 20; int num2 = 30; int num3 = 40; int num4 = 50;   /** * This method is used to concatenate strings and * primitive data types using + operator. * @author w3spoint */ public void concateOerations(){ //As expression executes from left to right and //num1, num2 both are primitive data types will result //into primitive, next argument is String and hence // will result into a string, next argument num3 // is a primitive type but as one of the two //operands is a string and hence result will be //a string, same is for num4. System.out.println(num1 + num2 + str1 + num3 + num4); } }   public class StringConcatenationExample2 { public static void main(String args[]){ //creating TestString object. TestString obj = new TestString(); //method call obj.concateOerations(); } }

## Output:

50jai4050

## 2. By concat() method:

This method concatenate argument string at the end of current string and return the resulting string.

Syntax: public String concat(String s).

## Example:

StringConcatenationExample3.java

/** * This program is used to show the concatenation * of strings by concat method. * @author w3spoint */ class TestString{ String str1 = "www."; String str2 = "w3spoint."; String str3 = "com";   /** * This method is used to concatenate strings using concat method. * @author w3spoint */ public void concateStrings(){ System.out.println(str1.concat(str2).concat(str3)); } }   public class StringConcatenationExample3 { public static void main(String args[]){ //creating TestString object. TestString obj = new TestString(); //method call obj.concateStrings(); } }

## Output:

www.w3spoint.com