问题
I have recently checked on my Java version. I ran the command java -version and I found out that I was using java version 1.7.0_09. But when I tried to check on C:\Program Files\Java\ directory, I don't seem to find the same version. I only see the following:
- j2re1.4
- jdk1.6.0_32
- jdk1.7.0_06
- jdk1.7.0_07
- jre6
- jre7
And so on...
My programs still run, but I'm just trying to compile everything manually, and understand how Java is being treated by the OS.
Another thing that is weird is, I tried to check on environment variable settings, and it does not say anything about jdk1.7.0_09.
Path:
- C:\Program Files\Common Files\Microsoft Shared\Windows Live;
- %SystemRoot%\system32;
- %SystemRoot%;
- %SystemRoot%\System32\Wbem;
- %SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;
- C:\Program Files\TortoiseSVN\bin;
- C:\Program Files\Windows Live\Shared;
- C:\eclipse\plugins\com.google.appengine.eclipse.sdkbundle_1.6.5\appengine-java-sdk-1.6.5\bin;
- C:\Program Files\Java\jdk1.7.0_07\bin;C:\Program Files\QuickTime\QTSystem\;
- %ANT_HOME%\bin
Just want to let you guys know that it somehow automatically became a jre.
The complete directory is C:\Users\User02\AppData\LocalLow\Sun\Java\jre1.7.0_09 and it's just got the file named lzma.dll.
But, I have another directory that says C:\Users\User02\AppData\LocalLow\Sun\Java\jdk1.7.0_07. The files inside it are:
- jdk1.7.0_07.msi
- sj170070.cab
- ss170070.cab
- st170070.cab
- and sz170070.cab
回答1:
It's possible to have many JRE side-by-side on a computer.
If the JRE is properly installed on Windows, informations about each version are stored in the registry. The installation process installs a special java.exe in the system PATH (%SYSTEMROOT%\System32). So you don't need to alter you PATH because this special java.exe will find the current JRE. From a command line, type java -version to display the current jre version installed.
With release 1.6, it's now possible to select a different JRE installation than the last one without any registry modification.
The JRE installation are listed in the registry in the key
HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment
Take this simple test class
public class ShowVersion {
public static void main(String args[]) {
System.out.println(System.getProperty("java.version"));
}
}
On a system, with 1.6 and 1.5 installed. If you type
> java ShowVersion
It's probably the 1.6 JRE that will be used since it's the last installed.
To force the 1.5 JRE instead, use this command line.
> java -version:"1.5" ShowVersion
If the bytecode is incompatible with the given JRE then .. it won't work, of course.
ref : technote java 6
You can always give the complete path to use a specific installation. Launching the JVM this way does not use the registry setting at all.
>"C:\Program Files\Java\j2re1.4.1_02\bin\java" -version
java version "1.4.1_02"
source : Select a particular JRE from the command line
回答2:
Adding the following will resolve your issue:
set JAVA_HOME="your jdk path"
set PATH=%JAVA_HOME%\bin;%PATH%.
Additionally if it does not work that means you have set the PATH for multiple java versions, include only the latest one and remove all from PATH variables.
回答3:
That AppData path in your comment isn't on your path (supposedly, anyway), so that's probably not what it's using. Unfortunately, there isn't a which command on Windows either.
If you edit your path and move the C:\Program Files\Java\bin directory to the very beginning of the list and it still prints 1.7.0_09, then somehow you have JDK7u9 in your JDK7u7 folder. If not, browse to all the other directories on your path and open them 1-by-1 until you find the appropriate java file. Fortunately for you, your path is much shorter than mine.
Note that when doing:
> java -version
It may also look for java.bat and other non-exe extensions, so keep an eye out for this while you're searching your path. Try running:
> java.exe -version
That way you know you're looking for an exe file.
One last thing you can try:
> "C:\Program Files\Java\jdk1.7.0_07\bin\java" -version
If this returns 1.7.0_09, then something happened that updated your JDK in-place, which isn't supposed to happen, AFAIK (but I could be wrong).
回答4:
In answer to the "actual" question:
Another thing that is weird is, I tried to check on environment variable settings, and it does not say anything about jdk1.7.0_09.
What happened here is that you installed jdk1.7.0_07 and then you auto-upgraded it. When that happens , it still uses the old folder name that you originally installed to.
After I install Java , I usually make a copy of the JDK directory and name it with the version number. Then, I can directly call a certain java like so:
@echo off
:: testjava.bat
set JAVA_HOME=C:\JDK1.x.xx
set PATH=%JAVA_HOME%\bin;%PATH%;.
java -version
pause
So, my recommendation is to set your JAVA_HOME system variable and PATH variable like I show above. This would override everything on your system so that your JDK of your choice is the default over the JRE.
来源：https://stackoverflow.com/questions/13734142/different-java-version-showing-on-command-line