1. Java SE 6, Platform Name and Version
TM
Numbers
At this release, the platform name has changed from J2SETM to JavaTM SE. The official name is
JavaTM Platform, Standard Edition 6.
Both version numbers (1.6.0 and 6) are used to identify this release of the Java Platform.
Version 6 is the product version, while 1.6.0 is the developer version. The number 6 is used to
reflect the evolving level of maturity, stability, scalability and security of Java SE.
Version 6 Used in Platform and Product Names
Version 6 is used in the platform and product names as given in this table:
Full Name Abbreviation
Platform name JavaTM Platform, Standard Edition 6 JavaTM SE 6
JavaTM SE Development Kit 6 JDKTM 6
Products delivered
under the platform
JavaTM SE Runtime Environment 6 JRETM 6
Due to significant popularity within the Java developer community, "JDK" continues to be the
acronym for the development kit, as does "JRE" for the runtime environment. Notice that "JDK"
stands for "Java SE Development Kit" (to distinguish it from the Java EE Development Kit
known as SDK). The name "Java Development Kit" is no longer used, and has not been offically
used since 1.1, prior to the advent of Java EE and Java ME.
Version 1.6.0 Used by Developers
Java SE keeps the version number 1.6.0 (or 1.6) in some places that are visible only to
developers, or where the version number is parsed by programs. As mentioned, 1.6.0 refers to
exactly the same platform and products numbered 6. Version numbers 1.6.0 and 1.6 are used
at:
java -version (among other info, returns java version "1.6.0")
java -fullversion (returns java full version "1.6.0-bxx")
javac -source 1.6 (is an alias for javac -source 6)
java.version system property
java.vm.version system property
@since 1.6 tag values

2. jdk1.6.0 installation directory
jre1.6.0 installation directory
http://java.sun.com/javase/6 website
Version 1.5.0 or 5.0?
Both version numbers "1.5.0" and "5.0" are used to identify this release of the Java 2 Platform
Standard Edition. Version "5.0" is the product version, while "1.5.0" is the developer version.
The number "5.0" is used to better reflect the level of maturity, stability, scalability and security
of the J2SE.
The number "5.0" was arrived at by dropping the leading "1." from "1.5.0". Where you might
have expected to see 1.5.0, it is now 5.0 (and where it was 1.5, it is now 5).
"Version 5.0" Used in Platform and Product Names
Version 5.0 is used in the platform and product names as given in this table:
Full Name Abbreviation
Platform name JavaTM 2 Platform Standard Edition 5.0 J2SETM 5.0
J2SETM Development Kit 5.0 JDKTM 5.0
Products delivered
under the platform J2SETM Runtime Environment 5.0 JRE 5.0
Due to significant popularity within the Java developer community, the development kit has
reverted back to the name "JDK" from "Java 2 SDK" (or "J2SDK"), and the runtime
environment has reverted back to "JRE" from "J2RE". Notice that "JDK" stands for "J2SE
Development Kit" (to distinguish it from the J2EE Development Kit). The name "Java
Development Kit" is no longer used, and has not been offically used since 1.1, prior to the advent
of J2EE and J2ME.
As before, the "2" in Java 2 Platform Standard Edition indicates the 2nd generation Java
platform, introduced with J2SE 1.2. This generation number is also used with J2EE and J2ME.
"Version 1.5.0" Used by Developers
J2SE also keeps the version number 1.5.0 (or 1.5) in some places that are visible only to
developers, or where the version number is parsed by programs. As mentioned, 1.5.0 refers to
exactly the same platform and products numbered 5.0. Version numbers 1.5.0 and 1.5 are used
at:

3. java -version (among other info, returns java version "1.5.0")
java -fullversion (returns java full version "1.5.0-b64")
javac -source 1.5 (javac -source 5 also works)
java.version system property
java.vm.version system property
@since 1.5 tag values
jdk1.5.0 installation directory
jre1.5.0 installation directory
http://java.sun.com/j2se/1.5.0 website (http://java.sun.com/j2se/5.0 also
works)
J2SE SDK/JRE Version String Naming
Convention
Developers may need to know a product's version string for various purposes, depending on
whether they are developing and deploying a product or downloading and integrating a
product.
The following table explains how to interpret SDK/JRE release version string information.
Note that this convention was not in effect prior to the 1.3.0 feature release. The output of
java -version has had the same format since 1.3.1
System Properties and the java -version Command
The output of the java -version command includes a product version identifier and a build
indentifier. This output is determined by the values of several system properties, and those
system properties can themselves be examined programmatically at runtime.
System Property Where Displayed in java -version
System Property Content
Name Output
Line one displays the product
java.version product version
version.

4. Line one displays the product
product version
version.
java.runtime.version product build
Line two displays the build
identifier
identifier.
Numbering Format Specifications
Every SDK/JRE release that is shipped has a product version string and a build identifier
associated with it. The general rules for setting either a version string or a build number string
are as follows. For more specific rules and examples, see the following table:
The content of the java.version system property must always be unique for each external
binary.
A separator is always used between different parts of the string so that ordering can be
determined programmically. (For example, a version string of "1.3.1beta" is not acceptable.
A version string of "1.3.1-beta" is acceptable.)
The format should be numeric and in lower case where applicable with a period "." within
the field itself and a dash "-" between fields.
A period "." separator indicates a major version.
An underbar "_" separator is used to indicate an update release.
A dash "-" separator is used to indicate a non-GA (non-FCS) release.
A GA (FCS) product version or build identifier must not contain a dash (-).
No asterik "*" or plus sign "+" is allowed, since these are used as wildcards for the matching
logic.
The content of the java.runtime.version system property can be expanded (beyond that of
the java.version system property) to include the build id.
All GA (FCS) versions are ordered based on the standard dot-notation. For example: 1.3.0 <
1.3.0_01 < 1.3.1 < 1.3.1_01.
Syntax Notation
Syntax notation used in the following table is:
Italics indicate syntax that varies.
<-identifier> indicates syntax that is present only for any non-GA (non-FCS) release.
The identifier is often used to represent a particular milestone, for example:
o early access
o beta
o rc1
J2SE Release and Version String Information

5. Release Example java -version
Description Version Numbering Format
Type Output Strings
Feature Contains new n.n.0<-identifier> The following output
functionality. indicates a GA (FCS) release
The final digit is always a having a build indentifier of
0. b24.
The -identifier is required
for any non-GA (non-FCS) java version "1.3.0"
release. Java(TM) 2 Runtime
A GA (FCS) release never Environment,
Standard Edition
has a -identifier. (build 1.3.0-b24)
Java HotSpot(TM)
Client VM (build
1.3.0-b24, mixed
mode)
Maintenance Contains n.n.n<-identifier> The following output
engineering indicates a beta,
focused bug The final digit is never a maintenance release
fixes. 0. having a build identifier of
The -identifier is required 09.
for any non-GA (non-FCS)
release. java version "1.3.1-
A GA (FCS) release never beta"
has a -identifier. Java(TM) 2 Runtime
Environment,
Standard Edition
(build 1.3.1-beta-
b09)
Java HotSpot(TM)
Client VM (build
1.3.1_05-ea-b01,
mixed mode)
Update Contains n.n.n_nn<-identifier> The output indicates an
customer early access, update
focused bug The first three digits are release having a build
fixes. identical to those of the identifier of b01.
feature or maintenance
release that is being java version
updated. "1.3.1_05-ea"
The two digits following Java(TM) 2 Runtime
Environment,
the underbar indicate the Standard Edition
update number. The (build 1.3.1_05-ea-
higher the number, the b01)
more recent the update. Java HotSpot(TM)

6. The -identifier is required Client VM (build
for any non-GA (non-FCS) 1.3.1_05-ea-b01,
mixed mode)
release.
A GA (FCS) release never
has a -identifier. The output indicates a
GA (FCS) update release
having a build identifier
of b02.
java version
"1.3.1_05"
Java(TM) 2 Runtime
Environment,
Standard Edition
(build 1.3.1_05-b02)
Java HotSpot(TM)
Client VM (build
1.3.1_05-b02, mixed
mode)
The output indicates an
early access, update
release having a build
identifier of b01.
java version
"1.4.0_03-ea"
Java(TM) 2 Runtime
Environment,
Standard Edition
(build 1.4.0_03-ea-
b01)
Java HotSpot(TM)
Client VM (build
1.4.0_03-ea-b01,
mixed mode)
The output indicates a
GA (FCS) update release
having a build identifier
of b04.
java version
"1.4.0_03"
Java(TM) 2 Runtime
Environment,
Standard Edition
(build 1.4.0_03-b04)
Java HotSpot(TM)
Client VM (build

7. 1.4.0_03-b04, mixed
mode)
Also see: