The String and StringBuffer Classes

Strings and the Java Compiler

Literals

In the Java language, you specify literal strings between double quotes just like in C and C++.

"Hello World!"

You can use literal strings anywhere you would use a String object. For example, System.out.println() accepts a String argument, so you could use a literal string in place of a String there.

System.out.println("And might I add that you look lovely today.");

You can also use String methods directly from a literal string.

int len = "Goodbye Cruel World".length();

Because the compiler automatically creates a new String object for every literal string it encounters, you can use a literal string to initialize a String.

String s = "Hola Mundo";

The above construct is equivalent to, but more efficient than, this one

String s = new String("Hola Mundo");

because the compiler ends up creating two Strings instead of one: first when the compiler encounters "Hola Mundo!", and second when it encounters new String().

Concatentation and the + Operator

In the Java language, you can use '+' to concatenate Strings together.

String cat = "cat";
System.out.println("con" + cat + "enation");

This is a little deceptive because, as you know, Strings are immutable objects; they can't be changed. However, behind the scenes the compiler uses StringBuffers to implement concatenation. The above example is compiled to:

String cat = "cat";
System.out.println(new StringBuffer.append("con").append(cat).append("enation"));

The String and StringBuffer Classes