Java Reference
In-Depth Information
A.1. Language, Library, and Virtual Machine Versions
Each new release of the Java platform potentially changes three things:
•
The language itself, through the addition of new keywords or ex-
tensions to the use of existing keywords
•
The libraries: new types and/or new methods on existing types
•
The virtual machine, and in particular the format of the compiled
classes that the virtual machine expects
Not every new platform release changes all threein particular, changes to
the class format occur rarely because of the major impact such changes
can have.
The compiler that comes with the Java Development Kit (JDK) tracks
changes to the language and virtual machine through the use of "source"
and "target" options that can be passed to it. By supplying an appropriate
source and target pair you can compile code that will run on current
or older versions of the virtual machineassuming the code is compatible
with the source version of the language chosen.
The different source versions and their approximate meaning are as fol-
lows:
•
1.1 The oldest recognized definition of the language, which in-
cluded the original language definition together with nested types
and blank final variables. This source version is no longer suppor-
ted by the compiler in the 5.0 release.
•
1.2 Introduced the
strictfp
modifier.
•
1.3 Same as 1.2; this version number was added for consistency.
•
1.4 Introduced
assert
.
