How does java locate a JAR file?

Question

The JAR file locates at C:\\Workbench\\jars\\antlr-4.4-complete.jar

The environment variables are:

CLASSPATH=.;C:\Workbench\jars\*
PATH=C:\Workbench\jars;...

I am trying with the following commands:

java -jar "C:\Workbench\jars\antlr-4.4-complete.jar"   <-- OK
java -jar antlr-4.4-complete.jar   <-- FAIL!
java org.antlr.v4.Tool  <-- OK

I am totally confused about the failed one. I am expecting the PATH variable will be looped through to locate the jar file. But it seems not. Why?

My guess is, the implementation of java -jar command line doesn't use the PATH variable for searching jar file. But still, why?

Answer 1

The PATH is for looking up the command to execute, in this case java will be looked up on the PATH .

You will need to supply either an absolute or relative path to java -jar because the terminal (bash/windows/zsh/etc...) will not expand arguments in this way. CLASSPATH is used by Java to look up further jars, but it expects a correct path to the initial jar as the first argument.