Why are there 2 Java platform binaries running for one java program on Windows 10?

Question

I have this simple java command line application

public static void main(String[] args) throws IOException {
        System.out.println("Hello World !");
        System.in.read();
}

When I start it on Windows 10, Windows Task Manager displays two instances of java.exe as subprocesses of the Windows Command Prompt process:

Java(TM) Platform SE binary from

C:\Program Files\Common Files\Oracle\Java\javapath_target_383000\java.exe

OpenJDK Platform binary from

C:\Program Files\Java\jdk-15.0.1\bin\java.exe

One should think one instance of the JVM should be enough to run this program, so why are there two ?

Edit: I compiled this program against a JDK 1.8.0 (instead of JDK 15.0.1) and now only the Java(TM) Platform SE binary shows up.

They are most probably two different running Java processes running two different Java programs! — Seelenvirtuose, Dec 22 '20 at 10:34
@Seelenvirtuose : no - because when the program exits, they both disappear — Angle.Bracket, Dec 22 '20 at 10:36
Yes, because one Java program only runs in one Java process! So it must be something else. Your assumption is wrong! — Seelenvirtuose, Dec 22 '20 at 10:38
There's definitely only one Java program running in this Windows command shell — Angle.Bracket, Dec 22 '20 at 10:47
What does `where java` print? Perhaps the javapath_target_383000 version is an unnecessary wrapper which launches the other. — DuncG, Dec 22 '20 at 10:56
`where java` prints `C:\Program Files\Java\jdk-15.0.1\bin\java.exe` — Angle.Bracket, Dec 22 '20 at 10:58

score 2 · Accepted Answer · answered Dec 22 '20 at 12:05

This is a feature of Oracle's installer for Java on Windows. The installer adds the folder C:\Program Files\Common Files\Oracle\Java\javapath_target to the PATH variable. This folder contains a symlink to a java.exe executable in another folder. This executable detects the location of the latest/configured JRE version by checking the registry and JAVA_HOME. Then it calls java.exe of the actual JRE. So the first java.exe is not a real JVM but a simple native app that gets executed, when you call java within the console. To avoid the usage of this mechanism simply replace the javapath_target folder with the folder of your JRE within the PATH environment variable. For a more detailed description see also this answer.

Why are there 2 Java platform binaries running for one java program on Windows 10?

1 Answers1