I would like to know what JAVA_HOME is. Where do I set the path of javac.exe and java.exe. It is in environment variables? When I compile a Java program from command prompt, how does the JVM find javac.exe?
What is JAVA_HOME? How does the JVM find the javac path stored in JAVA_HOME?
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10 Answers
JVM does not find java.exe. It doesn't even call it. java.exe is called by the operating system (Windows in this case).
JAVA_HOME is just a convention, usually used by Tomcat, other Java EE app servers and build tools such as Gradle to find where Java lives.
The important thing from your point of view is that the Java /bin directory be on your PATH so Windows can find the .exe tools that ship with the JDK: javac.exe, java.exe, jar.exe, etc.
JAVA_HOME is a environment variable (in Unix terminologies), or a PATH variable (in Windows terminology). A lot of well behaving Java applications (which need the JDK/JRE) to run, looks up the JAVA_HOME variable for the location where the Java compiler/interpreter may be found.
JAVA HOME is used for setting up the environment variable for JAVA. It means that you are providing a path for compiling a JAVA program and also running the same. So, if you do not set the JAVA HOME( PATH ) and try to run a java or any dependent program in the command prompt.
You will deal with an error as
javac : not recognized as internal or external command.
Now to set this, Just open your Java jdk then open bin folder then copy the PATH of that bin folder.
Now, go to My computer right click on it----> select properties-----> select Advanced system settings----->Click on Environment Variables------>select New----->give a name in the text box Variable Name and then paste the path in Value.
That's All!!
JAVA_HOME is an environment variable which is read by some development tools like Apache Tomcat, Apache Maven, Gradle, Jenkins etc. Usually, JAVA_HOME is set to point to JDK instead of JRE because these development tools need to use tools like compiler, debugger, document generator etc. which are only available in JDK since JDK is a development kit. JRE is only meant for running java applications. JDK = JRE + Development tools
Consumer facing Java applications don't read JAVA_HOME variable and they just need to know where the JVM is located and that's why JVM location (directory) needs to be added to the PATH variable. This is automatically done for you when you install Java software. Whenever you try to run a Java application by either double clicking on the app or through command line, your operating system reads PATH variable to locate and run JVM and it doesn't look for JAVA_HOME variable.
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