Question

So far as I know, when JRE executes an Java application,
the string will be seen as a USC2 byte array internally.
In wikipedia, the following content can be found.

Java originally used UCS-2, and added UTF-16 supplementary character support in J2SE 5.0.

With the new release version of Java (Java 7) ,
what is its internal character-encoding?
Is there any possibility that Java start to use UCS-4 internally ?

Answer 1

Java 7 still uses UTF-16 internally (Read the last section of the Charset Javadoc), and it’s very unlikely that will change to UCS-4. I’ll give you two reasons for that:

1. Changing from UCS-2=>UCS-4 would most likely meant that they would have to change the char primitive from a 16 bits type to a 32 bits type. Looking in the past at how high Sun/Oracle have valued backwards compatibility, a change like this is very unlikely.
2. A UCS-4 takes a lot more memory than a UTF-16 encoded String for most use cases.