ubuntu将openjdk7升级到openjdk8

在unbuntu14.04系统上安装 Open JDK 8 时遇到了如下问题：

$ sudo apt-get install openjdk-8-jdkReading package lists... DoneBuilding dependency tree       Reading state information... DoneE: Unable to locate package openjdk-8-jdk

解决方法：

As you can see I only have java 1.7 installed (on a Ubuntu 14.04 machine).

$ update-java-alternatives -ljava-1.7.0-openjdk-amd64 1071 /usr/lib/jvm/java-1.7.0-openjdk-amd64

To install Java 8, I did,

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

Afterwards, now I have java 7 and 8,

$ update-java-alternatives -ljava-1.7.0-openjdk-amd64 1071 /usr/lib/jvm/java-1.7.0-openjdk-amd64java-1.8.0-openjdk-amd64 1069 /usr/lib/jvm/java-1.8.0-openjdk-amd64

 

 How to switch between different versions?

   run the follwing command from the terminal:

   

$ sudo update-alternatives --config javaThere are 2 choices for the alternative java (providing /usr/bin/java).  Selection    Path                                            Priority   Status------------------------------------------------------------  0            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1071      auto mode  1            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1071      manual mode* 2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1069      manual modePress enter to keep the current choice[*], or type selection number:

 

As you can see I'm running open jdk 8. To switch to to jdk 7, press 1 and hit the Enter key. Do the same for javac,javap,javadoc as well with,:

$ sudo update-alternatives --config javac$ sudo update-alternatives --config javap$ sudo update-alternatives --config javadoc