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

途中でライセンスの許諾が必要
install-java-on-precise-1
install-java-on-precise-2
インストールの確認

$ java -version
java version "1.7.0_60"
Java(TM) SE Runtime Environment (build 1.7.0_60-b19)
Java HotSpot(TM) 64-Bit Server VM (build 24.60-b09, mixed mode)

参考: Install Oracle Java 7 in Ubuntu via PPA Repository ~ Web Upd8: Ubuntu / Linux blog