$ sudo add-apt-repository ppa:webupd8team/java
$ sudo apt-get update

Once PPA has been added and updated, now search for the packages with name oracle-java8 and install it as shown.

$ apt-cache search oracle-java8
$ sudo apt-get install oracle-java8-installer

If you have more than one Java installed on your system, you can install oracle-java8-set-default package to set Java 8 as default as shown.

$ sudo apt-get install oracle-java8-set-default

 # java -version
java version "1.8.0_161"
Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)
root@zbook /usr/local/netbeans-8.2/bin
 # 

$ chmod +x netbeans-8.2-linux.sh 
$ ./netbeans-8.2-linux.sh