Skip to content

install-java.md

Latest commit

 

History

History
59 lines (46 loc) · 1.85 KB

install-java.md

File metadata and controls

59 lines (46 loc) · 1.85 KB
Raw

Install Java (JDK/JRE) on Ubuntu

1. What is it / What is it for?

Instructions for installing a Java runtime/compiler — either OpenJDK (free, default) or Oracle JDK (legacy, license-restricted) — and registering it with update-alternatives.

  • Running Java applications (e.g. Weka, ELAN, Android tooling) or building Java code.
  • Setting JAVA_HOME / CLASSPATH and making java/javac available system-wide.

2. How to download / install

OpenJDK (recommended)

sudo apt-get install openjdk-17-jdk     # or openjdk-11-jdk / openjdk-8-jdk
java -version

Oracle Java (older approach — PPA may be dead)

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer

Manual Oracle JDK (tarball)

sudo mkdir -p /usr/lib/jvm/jdk1.7.0
sudo mv jdk1.7.0_xx/* /usr/lib/jvm/jdk1.7.0/

3. How to use

Register with update-alternatives

sudo update-alternatives --install /usr/bin/java  java  /usr/lib/jvm/jdk1.7.0/jre/bin/java  1
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0/bin/javac    1
sudo update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.7.0/jre/bin/javaws 1
# make it the default:
sudo update-alternatives --set java  /usr/lib/jvm/jdk1.7.0/jre/bin/java
sudo update-alternatives --config java     # or pick interactively
java -version

Environment variables (add to ~/.bashrc)

export JAVA_HOME=/home/abc/jdk1.7.0_37
export PATH=$PATH:$JAVA_HOME/bin:$JAVA_HOME/jre/bin
export CLASSPATH=.:$JAVA_HOME/lib:$JAVA_HOME/jre/lib

Then source ~/.bashrc.

Browser plugin (legacy, 32/64-bit)

mkdir -p ~/.mozilla/plugins
ln -s /usr/lib/jvm/jdk1.7.0/lib/amd64/libnpjp2.so ~/.mozilla/plugins/    # 64-bit
# ln -s /usr/lib/jvm/jdk1.7.0/lib/i386/libnpjp2.so ~/.mozilla/plugins/   # 32-bit