The java.lang.String class provides a way to work with a sequence of characters.

String is a class(not a primitive ) and also you can say a reference type.

• Primitive Types (int, float, etc) : They directly hold the values in memory.
• Reference Type (String, Array, List, object) : These store the memory addresses (references) of an object in the heap

Ways to Create a String Object.

a) Using the new keyword.

String s1 = new String ("Hello");

b) Using string literals.

String s2 = "Hello"

Interning

String s = "Hello"

The String literal “Hello” is stored in the String Pool ( a part of the Heap memory). The variable ‘s’ holds a reference (a memory address) pointing to the location of “Hello” in the String Pool.

String s2 = "Hello";

Here ‘s2‘ will reference the same object in the String Pool as ‘s‘ as String literals with the same values will be shared.

Interning refers to a mechanism for optimizing memory usage by ensuring that identical String objects share a single instance in a special memory area called the String Pool. This process avoids creating duplicate String Objects with the same content.

So when a String literal is created, the JVM first checks the pool:

• If a literal already exists in the pool, a reference to the existing object is returned.
• If a literal doesn’t exist. it is added to the pool and a reference to the new object is returned.

Explicit Interning: The intern() method in the String class forces a String Object to be added to the pool.

Lets see how to initialize using two methods:

#String Literal Initialization
String a = "Hello"
String b = a;
String c = "Hello";

Here all the variables share the same reference.

(a==b) ; #True
(a==c) ; #True
(b==c) ; #True

#Using the new Keyword
char[]text = {'H','e','l','l','o'};
String a = new String(text); #creates a new String object and does not reuse the interned "Hello" because of using the new keyword.
String b = new String("Hello"); #Creates a new String Object
(a == b); #false
String c = a.intern();
(c == d); #True

The intern() method ensures that String object refers to the interned version in the String Pool.