If we want to programmatically determine what version of the Java Runtime Environment

(JRE) is being used to execute a given application then, we can get the version via the following code illustrates:


String ver = System.getProperty("java.version"));
System.out.println("This program is running under JRE version " + ver);</code>

if (ver.startsWith("1.5")) {
     // Pseudocode.
     do something appropriate for newer versions of Java ...

else {
     // Pseudocode.
    do something the pre-5.0 way ...

Some of the java System Properties based on JDK 1.5 are given as follows:

Key Description of Associated Value

java.version Java Runtime Environment version
java.vendor Java Runtime Environment vendor
java.vendor.url Java vendor URL
java.home Java installation directory
java.vm.specification.version Java Virtual Machine specification version
java.vm.specification.vendor Java Virtual Machine specification vendor
java.vm.specification.name Java Virtual Machine specification name
java.vm.version Java Virtual Machine implementation version
java.vm.vendor Java Virtual Machine implementation vendor
java.vm.name Java Virtual Machine implementation name
java.specification.version Java Runtime Environment specification version
java.specification.vendor Java Runtime Environment specification vendor
java.specification.name Java Runtime Environment specification name
java.class.version Java class format version number
java.class.path Java class path
java.library.path List of paths to search when loading libraries
java.io.tmpdir Default temporary file path
java.compiler Name of JIT compiler to use
java.ext.dirs Path of extension directory or directories
os.name Operating system name
os.arch Operating system architecture
os.version Operating system version
file.separator File separator (/ on Unix)
path.separator Path separator (: on Unix)
line.separator Line separator (\n on Unix)
user.name User’s account name
user.home User’s home directory
user.dir User’s current working directory

The following table describes some of the most important system properties BASED on JDK 1.6

Key Description of Associated Value

"file.separator" Character that separates components of a file path. This is
/” on UNIX and “\” on
"java.class.path" Path used to find directories and JAR archives containing class files.
Elements of the class path are separated by a platform-specific character specified in the path.separator property.
"java.home" Installation directory for Java Runtime Environment (JRE)
"java.vendor" JRE vendor name
"java.vendor.url" JRE vender URL
"java.version" JRE version number
"line.separator" Sequence used by operating system to separate lines in
text files
"os.arch" Operating system architecture
"os.name" Operating system name
"os.version" Operating system version
"path.separator" Path separator character used in java.class.path
"user.dir" User working directory
"user.home" User home directory
"user.name" User account name