String Concatenation in Java

String Concatenation in Java: String Concatenation in Java can be possible by two ways,

Example Program:

[java]
package com.ngdeveloper.com;

public class StringConcatenation {

public static void main(String[] args) {
String hVariable = "hello ";
String wVariable = "world";
String hwVariable = hVariable.concat(wVariable);

String a = "java";
String b = "domain";
String javadomain = a + b;

System.out.println("String concatenation using concat() : "+hwVariable);
System.out.println("String concatenation using + operator : "+javadomain);
}

}

[/java]

Output:
String concatenation using concat() : hello world
String concatenation using + operator : javadomain

Difference between + and concat():

Using + operator:

1. Any type of variable can be concatenated, it is not mandatory to be a string variable.

[java]

String firstVar = "Java";
int secVar = 11;
String plusConcat = firstVar + secVar;
System.out.println(plusConcat); // prints Java11
[/java]

2. String can be null and it will not throw null pointer exception.

[java]
String myVar = null;
String plus = myVar + "java";
System.out.println(plus); // prints nulljava
[/java]

Using Concat():

1. Argument must be string for concatenation using concat()

[java]
a.concat(11) //it is not possible
[/java]

2. String must not be null, if it is null then it will throw null pointer exception.

[java]
String myVar = null;
String value = "java";
System.out.println(myVar.concat(value)); // throws null pointer exception
[/java]