Monday, July 5, 2010

What is java.home?

Target Audience: Beginners
When a java program runs, the java runtime environment (JRE- who runs any java program) sets some system properties for its own use and java.home is one of those system properties. The java.home is referencing the JRE home directory E.g: C:\Tools\jdk1.5.0_04\jre.

People tend to confuse with JAVA _HOME and java.home. They are different. JAVA _HOME is set by the user ( me or you) to reference JDK’s home directory. E,g: C:\Tools\jdk1.5.0_04\

Following are the system properties that java sets.
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 Virtual Machine specification name
java.vm.version Java Virtual Machine implementation version
java.vm.vendor Java Virtual Machine implementation vendor Java Virtual Machine implementation name
java.specification.version Java Runtime Environment specification version
java.specification.vendor Java Runtime Environment specification vendor 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 Default temp file path
java.compiler Name of JIT compiler to use
java.ext.dirs Path of extension directory or directories 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's account name
user.home User's home directory
user.dir User's current working directory

public class SystemExample {
public static void main(String[] args) {
System.out.println("java.home :" + System.getProperty("java.home"));
System.out.println("java.vm.version :" + System.getProperty("java.vm.version"));
System.out.println(" :" + System.getProperty(""));
System.out.println("os.version :" + System.getProperty("os.version"));
System.out.println(" :" + System.getProperty(""));

The output will be similar to this

java.home :C:\Tools\jdk1.5.0_04\jre
java.vm.version :1.5.0_04-b05 :Windows XP
os.version :5.1 :kannan

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