'java -version' command shows different version than what I have

Question

In my C:\Program files\java folder I have three folders:

jdk1.6.0_45
jre6
jre7

However typing the command java -version in the command prompt gives the following output:

java version "1.7.0_51"

How does that make sense? I think it should have outputed jdk1.6.0_45. How can this be explained?

Why do you think it should have printed a version corresponding to Java 6? — Matt Ball
– Matt Ball, Commented May 1, 2014 at 22:33
The java command invokes the Java interpreter not the compiler so it would be found in a JRE package (i.e. jre7). — Elliott
– Elliott, Commented May 1, 2014 at 22:33
@Elliott If I want to compile using JDK7, should I be able to do that? — Aviv Cohn
– Aviv Cohn, Commented May 1, 2014 at 22:36
@Prog You need to install a JDK7 package (just go download latest version!) and then use the javac command to compile. :) — Elliott
– Elliott, Commented May 1, 2014 at 22:37
@Elliott I see. What does it actually mean to compile using JDK X instead of JDK Y? Is it that a program compiled with JDK X will be able to run on JRE X and a program compiled with JDK Y will be able to run on JRE Y? — Aviv Cohn
– Aviv Cohn, Commented May 1, 2014 at 22:39

Elliott · Accepted Answer · 2014-05-01 23:08:04Z

1

Already answered this in the comments thread but for future reference:

Broadly speaking, the JDK package determines the version of the Java compiler (javac) you have and the JRE package determines the version of the Java interpreter (java) you have.

The version that is run when you type java or javac in the command line is the version that is listed in your PATH environmental variable, which will generally point to the newest version from the newest package (the Java installer does this for you).

The JDK will install the corresponding JRE at the same time so you'll have the same version of java and javac by just installing the latest JDK.

edited May 1, 2014 at 23:08

answered May 1, 2014 at 22:57

Elliott

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Aviv Cohn Over a year ago

After installing a new JDK (and JRE), do I need to 'tell Java' to 'connect' to the new JDK? Or is it enough to just download and install it?

antont · Accepted Answer · 2014-05-01 22:33:10Z

1

Perhaps it finds have from inside the jre7 folder? You can check your PATH to see where it finds executables.

answered May 1, 2014 at 22:33

antont

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Peter Lawrey · Accepted Answer · 2014-05-01 22:32:41Z

0

You have a jre7 so I assume it is update 51

Java takes the newest version by default.

answered May 1, 2014 at 22:32

Peter Lawrey

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Totoro · Accepted Answer · 2014-05-01 22:55:29Z

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It could also be if and where the JAVA_HOME ENV points to.

answered May 1, 2014 at 22:55

Totoro

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