How do I install Java?

Note: WebUpd8 team's PPA has been discontinued with effective from April 16, 2019. Thus this PPA doesn't have any Java files. More information can be found on PPA's page on Launchpad. Hence this method no longer works and exists because of historical reasons.

Detailed instructions to install Oracle Java 8 are updated in the blog here.

You can also use below commands for a quick answer -

sudo add-apt-repository ppa:webupd8team/java

sudo apt-get update

sudo apt install oracle-java8-set-default

javac -version

Please do note that you can also install openJDK which is also maintained by Oracle.

UPDATE: Since Ubuntu 16.04 you can install this without the ppa via

$> sudo apt-get update
$> sudo apt-get install openjdk-8-jdk

LEGACY ANSWER:

For Ubuntu < 16.04 there was no official package for Java 8 from OpenJDK ( the open source version ), but you can install it via this PPA by running:

$> sudo add-apt-repository ppa:openjdk-r/ppa
$> sudo apt-get update
$> sudo apt-get install openjdk-8-jdk

# current java release - get both jdk / jre download here

sudo mkdir /usr/local/java

cd /usr/local/java

# remove previous installs if any

sudo rm -rf /usr/local/java/jdk*
sudo rm -rf /usr/local/java/jre*

# move downloaded/expanded dirs into /usr/local/java

sudo mv ~/jdk* /usr/local/java/
sudo mv ~/jre* /usr/local/java/

cd /usr/local/java/

# create symbolic links

sudo ln -s jdk*  jdk
sudo ln -s jre*  jre

# ONLY need to do below on fresh ubuntu install - IGNORE if previously installed any java version as its already in place

# setup symlinks :

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/local/java/jre/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/local/java/jdk/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jre/bin/javaws" 1
sudo update-alternatives --set java /usr/local/java/jre/bin/java
sudo update-alternatives --set javac /usr/local/java/jdk/bin/javac
sudo update-alternatives --set javaws /usr/local/java/jre/bin/javaws

Finally, put these in your ~/.bashrc

export JAVA_HOME=/usr/local/java/jdk
export PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JRE_HOME=/usr/local/java/jre
export PATH=$PATH:$HOME/bin:$JRE_HOME/bin

now you're locked and loaded ;-)

If you are missing Java in Firefox, then

plug=~/.mozilla/plugins/libnpjp2.so && 
test -e $plug && readlink -f $plug || 
  ln -f -s `find ~ -wholename '*jdk*lib*libnpjp2.so' -or -wholename '*jre*lib*libnpjp2.so' | head -n 1` `dirname $plug` && 
ls -la $plug

This script will overwrite libnpjp2.so even if it exists, but points to wrong file (for example, the symlink is broken).

I made a text-based Java installer using terminal commands. It uses wget, tar, update-alternatives, and ln. It will install the Oracle JRE with the Firefox plugin.

You can download the installer from Google Drive here. Then put it in your home folder, open Terminal and type bash Install. Then it will run the installer in Terminal. It uses sudo, so you will need to type your password after it downloads. Also, this is the 64-bit version, so I will add the 32 bit later.

Note: WebUpd8 team's PPA has been discontinued with effective from April 16, 2019. Thus this PPA doesn't have any Java files. More information can be found on PPA's page on Launchpad. Hence this method no longer works and exists because of historical reasons.

Oracle Java 8 was just released (stable). To install it in Ubuntu, you can use the WebUpd8 Java PPA:

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

The PPA itself doesn't provide Oracle Java 8 binaries (that's not allowed by the Oracle Java license). Instead, an installer is used that automatically downloads and installs Oracle Java 8. Using this PPA, you'll also receive automatic Java 8 updates.

More information and some tips on using / further configuring Oracle Java 8 @ WebUpd8 is in Install Oracle Java 8 In Ubuntu Via PPA Repository [JDK 8].

Note: WebUpd8 team's PPA has been discontinued with effective from April 16, 2019. Thus this PPA doesn't have any Java files. More information can be found on PPA's page on Launchpad. Hence this method no longer works and exists because of historical reasons.

Open your terminal with Ctrl+Alt+T and:

Now this will install the latest Java version

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer

Installing OpenJDK - Recommended

The simplest way to install Java on Ubuntu is to use OpenJDK. This will work fine for most people. To install it, click on the small button with the Ubuntu logo on it, as shown in the screenshot below.

After opening the Dash Home, you need to type in Terminal. Click on the icon that is circled in the screenshot below.

This will open the Terminal, which is Ubuntu's version the the Windows Command prompt, though the Terminal has many more features. Now, copy and paste the following command into the Terminal window. You will need to use ControlShiftV to paste text into the terminal.

sudo apt-get install -y openjdk-7-jre openjdk-7-jdk

You will need to enter your password to use this command. Although it will not show up in the Terminal, it will still be entered when you type it. After running this command, you will be set up to run and develop Java applications.

Installing Oracle Java

OpenJDK works fine for most people, but if you play Minecraft, you will want to use Oracle Java instead. To install Oracle Java, run the command below one at a time in the Terminal.

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer

This will download Java from Oracle's website, and install it for you.

• Are PPA's safe to add to my system and what are some "red flags" to watch out for?

Unfortunately, because of issues with its license, Oracle Java is no longer distributed within the official Ubuntu repositories. You have two main options: either try OpenJDK -- an open source replacement for Oracle Java -- or proceed with the "manual" installation (which is exactly what you were trying to do). Both these options are described on the help wiki: https://help.ubuntu.com/community/Java. This page also include some other alternatives that, depending on your needs, you may find more suitable.

Just a side note: most of the time, with Ubuntu, you should not download software from the Internet, but rather use the Ubuntu Software Center. The software you'll find there is ensured to be stable, safe and to respect the standard conventions of the system. Oracle Java is just an exception to this rule.

There are a few ways to install Java in Ubuntu:

Install OpenJDK (The open source equivalent to Sun's Java) directly from Ubuntu Software Center. All you need to do is search for Java. That tends to work as is for me.

If you need Sun's Java, say if you want to play Minecraft, you download the JRE as you described from Java.com, but make sure your .bin-file can be executed. You do that by opening a terminal and typing the following (I will assume you have it in your Downloads folder so change the cd line accordingly if that's not where it is):

cd /home/user/Downloads
sudo chmod +x jre-6u31-linux-i586.bin

Then, you should be able to close your terminal, right click on your .bin-file and select "Execute", which should run the installer. If this is not an option, just do the following from terminal (in the same folder as the two other actions):

./jre-6u31-linux-i586.bin

That simply runs the specified file and if you successfully typed in the two first lines, the installation.

Note: WebUpd8 team's PPA has been discontinued with effective from April 16, 2019. Thus this PPA doesn't have any Java files. More information can be found on PPA's page on Launchpad. Hence this method no longer works and exists because of historical reasons.

For installing Oracle Java 7:

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo mkdir -p /usr/lib/mozilla/plugins #just in case, this will be added to the package in the next version
sudo apt-get install oracle-jdk7-installer

• Are PPAs safe to add to my system and what are some "red flags" to watch out for?

Just go to Aplications --> Ubuntu software center and then search for Java.

Installing OpenJDK is not enough for enabling Java in browsers. You'll also need to install the icedtea-7-plugin package:

A restart of the browser might be required.