Where is the new Object of String created when we concat using + operator

Question

I know this might be quite basic and probably pretty straight forward but i cannot clearly understand what will happen in this situation, so, here it goes.

In the following code:

String str1 = "Hello";
String str2 = "World";
String str3 = new String("HelloWorld");
String str4 = str1 + str2;

i know that str1 and str2 will create an object "Hello" and "World" respectively inside the String Constant Pool. While for str3 a new object is created outside the String Constant Pool which is pointing to "HelloWorld" that is created inside String Constant Pool.

My question is, what will happen if i concat 2 or more string (using '+' or concat() method)?

Will a new object be created outside the pool just like in the case of String str3 or will str4 point directly at the object "HelloWorld" inside the String Constant Pool

PS : And IF it is the case similar as creation of new object outside the pool, then how does it happen without using the new keyword?

Answer 1

First of all String s = new String("abs"); It will create two objects, one object in the pool area and another one in the non-pool area because you are using new and as well as a string literal as a parameter.

String str1 = "Hello";
String str2 = "World";
String str3 = new String("HelloWorld");
String str4 = str1 + str2;

Till now you have five String objects, four in String Constant Pool and one in Heap. So your str4 is a new object altogether inside the String Pool, Please check the below code also,

 String str5="HelloWorld"; //This line will create one more String Constant Pool object because we are using the variable name as str5.
 String str6="HelloWorld";////This line will not create any object, this will refer the same object str5.

For test

System.out.println(str3==str4); //false
System.out.println(str4==str5);//false
System.out.println(str5==str6);//true