Explain the concept of string interning and why it is used in programming.

String interning is the process of storing a single copy of each unique string constant in memory, so that all references to the same string point to the same object.

This is used for:

• Saving memory, especially when there are many identical strings.
• Speeding up string comparison operations — instead of comparing character by character, it is enough to compare references.

In C#, string interning is implemented via the String.Intern() method. For example:

string a = "hello";
string b = String.Intern(new string(new char[] { 'h', 'e', 'l', 'l', 'o' }));

bool sameReference = Object.ReferenceEquals(a, b); // true

Here, a and b point to the same string in the intern pool.