Ubuntu-为什么我有那么多Oracle Java 7，应该使用哪一个？

Question

I just want to use Oracle's Java 7 JVM to make sure Eclipse is running as fast as it can. What is going here? Which one should I choose?

$ sudo update-alternatives --config java
There are 4 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                            Priority   Status
------------------------------------------------------------
  0            /usr/lib/jvm/java-7-oracle/jre/bin/java          1055      auto mode
  1            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1051      manual mode
* 2            /usr/lib/jvm/java-7-oracle/bin/java              1         manual mode
  3            /usr/lib/jvm/java-7-oracle/jre/bin/java          1055      manual mode
  4            /usr/lib/jvm/jre1.7.0/bin/java                   3         manual mode

Press enter to keep the current choice[*], or type selection number: 

Answer 1

This ...

0 /usr/lib/jvm/java-7-oracle/jre/bin/java

... is Oracle JDK's bundled JRE. This ...

1 /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java

... is Open JDK's bundled JRE. This ...

2 /usr/lib/jvm/java-7-oracle/bin/java

... is Oracle's JDK. This ...

3 /usr/lib/jvm/java-7-oracle/jre/bin/java

... is a repeat of number 1. This ...

4 /usr/lib/jvm/jre1.7.0/bin/java

... is an independent JRE (probably Oracle`s but I don't know because it doesn't say on the file path).

I will for the moment assume you know the different between JDK and JRE. Every JDK has a bundled JRE. They will be usually in the JDK install folder name JRE.

Oracle's JDK and JRE is a bit better than OpenJDK so I suggest you use 0 for runtime and 2 for development.

Answer 2

Try running each of those path with -version to see what they say to be. Say:

$ /usr/lib/jvm/java-7-oracle/jre/bin/java -version

You can then check with aptitude search jdk to see what packages you have installed, for example, and try to match them.