What is the character encoding of String in Java?

Question

I am actually confused regarding the encoding of strings in Java. I have a couple of questions. Please help me if you know the answer to them:

1) What is the native encoding of Java strings in memory? When I write String a = "Hello" in which format will it be stored? Since Java is machine independent I don't think the system will do the encoding.

2) I read on the net that "UTF-16" is the default encoding but I got confused because say when I write that int a = 'c' I get the number of the character in the ASCII table. So are ASCII and UTF-16 the same?

3) Also I wasn't sure on what the storage of a string in the memory depends: OS, language?

Answer 1

1. Java stores strings as UTF-16 internally.

2. "default encoding" isn't quite right. Java stores strings as UTF-16 internally, but the encoding used externally, the "system default encoding", varies from platform to platform, and can even be altered by things like environment variables on some platforms.

   ASCII is a subset of Latin 1 which is a subset of Unicode. UTF-16 is a way of encoding Unicode. So if you perform your int i = 'x' test for any character that falls in the ASCII range you'll get the ASCII value. UTF-16 can represent a lot more characters than ASCII, however.

3. From the java.lang.Character docs:

   The Java 2 platform uses the UTF-16 representation in char arrays and in the String and StringBuffer classes.

   So it's defined as part of the Java 2 platform that UTF-16 is used for these classes.