Why is String a class?

If it can be initiated with just

String s = "Hello"; 

then why is it a class? Where's the parameters?

5 Answers

Given that String is such a useful and frequently used class, it has a special syntax (via a string literal representation: the text inside "") for creating its instances, but semantically these two are equivalent:

String s = "Hello"; // just syntactic sugar String s = new String("Hello"); 

Behind the hood both forms are not 100% equivalent, as the syntax using "" tries to reuse strings from Java's string pool, whereas the explicit instantiation with new String("") will always create a new object.

But make no mistake, either syntax will produce a reference to an object instance, strings are not considered primitive types in Java and are instances of a class, like any other.

String s = "Hello"; 

is just syntactical sugar. It's actually implemented as a reference type. (It's an immutable reference type, so you can't change it)

From the §4.3.3 of the Java Specification:

String literals are references to instances of class String.

And from §3.10.5:

A string literal is a reference to an instance of class String

String s = "Hello"; 

JVM treats it as:

String s = new String("Hello"); and interns it to String pool as String literal.

The line you have in the example is creating a String object. There aren't any parameters in the traditional sense that you are thinking of.