Visit http://www.oracle.com/technetwork/java/javase/downloads/index.html, click the download button of Java Platform (JDK) 8. Click to Accept License Agreement, download jdk-8-linux-arm-vfp-hflt.tar.gz for Linux ARM v6/v7 Hard Float ABI.
Open terminal, enter the command to copy the download file to Raspberry Pi using scp.
$ scp jdk-8-linux-arm-vfp-hflt.tar.gz pi@<Raspberry Pi>:
Log-in Raspberry Pi, enter the command to extract jdk-8-linux-arm-vfp-hflt.tar.gz to /opt directory.
$ sudo tar zxvf jdk-8-linux-arm-vfp-hflt.tar.gz -C /opt
Set default java and javac to the new installed jdk8.
$ sudo update-alternatives --install /usr/bin/javac javac /opt/jdk1.8.0/bin/javac 1
$ sudo update-alternatives --install /usr/bin/java java /opt/jdk1.8.0/bin/java 1
$ sudo update-alternatives --config javac
$ sudo update-alternatives --config java
After all, verify with the commands with -verion option.
$ java -version
$ javac -version
