Ubuntu安装jdk的步骤

1、先检查是否已经安装jdk

java -version

若显示

The program 'java' can be found in the following packages:
* default-jre
* gcj-4.8-jre-headless
* openjdk-7-jre-headless
* gcj-4.6-jre-headless
* openjdk-6-jre-headless
Try: apt-get install <selected package>

则表示java未安装

2、如上所示，则需安装jre

sudo apt-get install default-jre

3、再安装jdk
（1）安装open-jdk

sudo apt-get install default-jdk

（2）安装oracle-jdk

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