Run the following commands to install JAVA openjdk 15

zypper up
zypper ar http://download.opensuse.org/repositories/Java:/Factory/openSUSE_Leap_15.2/ java
zypper mr -p 70 java
zypper refresh
zypper in java-15-openjdk
java --version

If a JAVA version is already installed on your system before the installation of openjdk 15, use alternatives command to change the java version used by your system.

alternatives --config java                        # In case of upgrade: Switches the links to point to the new version
# logout and login again to have the environment variables defined.

• Use the existing package installer (apt or yum for example) to install latest GA version of JAVA OpenJDK (currently 15)
• Example on CentOS:

yum install java-latest-openjdk-headless.x86_64   # Installs the latest OpenJDK binaries
alternatives --config java                        # In case of upgrade: Switches the links to point to the new version
java -version                                     # Check you run the latest version 

• Or download the Linux/x64 archive from https://jdk.java.net/ and decompress it in your usual Java install path and update /usr/bin/java link
• Refer to the online documentation specific to your Linux distribution