How to replace stock java with downloaded binary?

Question

In Debian Stable the latest openjdk version available is 17.

$ which -a java
/usr/bin/java
/bin/java
$ java --version
openjdk 17.0.8 2023-07-18
OpenJDK Runtime Environment (build 17.0.8+7-Debian-1deb12u1)
OpenJDK 64-Bit Server VM (build 17.0.8+7-Debian-1deb12u1, mixed mode, sharing)

I wanted to test out 21 which will be released soon so I downloaded the binaries directly.

$ curl https://download.java.net/java/GA/jdk21/fd2272bbf8e04c3dbaee13770090416c/35/GPL/openjdk-21_linux-x64_bin.tar.gz
$ tar -xzf openjdk-21_linux-x64_bin.tar.gz
$ cd jdk-21
$ ./bin/java --version
openjdk 21 2023-09-19
OpenJDK Runtime Environment (build 21+35-2513)
OpenJDK 64-Bit Server VM (build 21+35-2513, mixed mode, sharing)
$ which -a java
/usr/bin/java
/bin/java
$ java --version
openjdk 17.0.8 2023-07-18
OpenJDK Runtime Environment (build 17.0.8+7-Debian-1deb12u1)
OpenJDK 64-Bit Server VM (build 17.0.8+7-Debian-1deb12u1, mixed mode, sharing)

I would like all my scripts to use the new java binaries without having to manually edit all java entries in them. That is, when invoking java I would like the new binaries to run. Can I replace stock java by simply copy pasting to /usr/bin/ and /bin/? That is, will this work?

$ mv ./bin/* /usr/bin/
$ mv ./bin/* /bin/

Do I also need to copy other folders in jdk-21 such as conf and lib? Can replacing stock java cause any side effects?

Answer 1

Simply modify PATH so that realpath ./bin comes first.

For example, in ~/.bashrc, you can use export PATH="/home/yyhh344/Downloads/java-21/bin:$PATH".

You may also need to set JAVA_HOME and other Java environment variables depending on your usage.