What's the Role of Java's `intern()` Method in String Management?

String Literal Interning and the intern() Method

Java boasts a useful feature known as String literal interning, which automatically stores String literals in the String pool. However, the intern() method remains an important tool for managing Strings.

The intern() method is intended to fetch a String from the pool if it exists there. If not, a new String object gets added to the pool, and a reference to it is returned.

While String literals are interned by default, the intern() method becomes valuable for Strings created with new String(). Consider the following example:

String s1 = "Rakesh";
String s2 = "Rakesh";
String s3 = "Rakesh".intern();
String s4 = new String("Rakesh");
String s5 = new String("Rakesh").intern();

Using the == operator for these variables produces the following results:

s1 and s2 are same
s1 and s3 are same
s1 and s5 are same

Here, only s4 behaves differently because it was explicitly created with new and not interned.

In conclusion, the intern() method ensures that only a single immutable String instance is returned from the String constant pool, regardless of how the String is created, except when using new and omitting the intern() call.

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