Can't install Java JDK

Can't install Java JDK - java

Ok, this is embarrassing, but I can't install Java. I have no experience in Java so any help appreciated.
So as ussual I install Java JDK (The JRE I think is already there before) I have jre7 and jdk1.8.0.0_05
I have install it, but Java still not in my computer
Here's some desperate cmd check
>C:\>WHERE java
>INFO: Could not find files for the giving pattern
>C:\>java
>'java is not recognized as an internal or external command, operable program or batch file.
Where my java folder is C:\Program Files (x86)\Java\jdk1.8.0.0_5
On my desperation I created the variable JAVA_HOME on the given directory. Afterward, I tried this.
>C:\>echo %JAVA_HOME%
%JAVA_HOME%
I was expecting the cmd to echo the directory.
The variable PATHEXT has the following in it:
.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
Clariffication:
I tried to reinstall the Java Jdk Installer with Windows Installer, but no luck.
If this matters, I'm running from Windows 7.
I tried to learn from Here
After closer inspection, I can run java and javac after going all the way into the directory (so inputing java outside the bin will do nothing good)

Add C:\Program Files (x86)\Java\jdk1.8.0.0_5\bin to your PATH variable
Here is how mine is

I think you may have not added JAVA_HOME environment variable, and/or to PATH environment variable neither.
Give a read to this article
http://www3.ntu.edu.sg/home/ehchua/programming/howto/jdk_howto.html

Regarding you last comment, i think you should put the java directory right infront of all the other directory because, if you were to install another version of java it might not be used if you place it behind.
(For Advanced Users Only)
I suggested that you place the JDK bin directory in front of "c:\windows\system32" and "c:\windows". This is because some Windows systems may have an out-dated copy of JDK/JRE in these directories. Do a search for "java.exe", and you will be amazed by the findings.
You could read "Java Applications and Environment Variable" for more discussions about PATH environment variable.
I also recommend that you define an environment variable called JAVA_HOME, which contains the JDK installed directory, and include the JDK bin directory in the PATH via JAVA_HOME, i.e., PATH=%JAVA_HOME%\bin;.....

Related

can't install R package due to java error [duplicate]

I went to the Environment Variables in 'System' in the control panel and made two new variables, one for user variables and one for system variables. Both were named JAVA_HOME and both pointing to
C:\Sun\SDK\jdk\bin
But for some reason, I still get the below error when running a Java command...
BUILD FAILED
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:161: The following error occurred while executing this line:
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:141: The following error occurred while executing this line:
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:137: Please set java.home to a JDK installation
Total time: 1 second
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish>lib\ant\bin\ant -f setup.xml
Unable to locate tools.jar. Expected to find it in C:\Program Files\Java\jre6\lib\tools.jar
Buildfile: setup.xml
How can I fix this problem?

Find JDK Installation Directory
First you need to know the installation path for the Java Development Kit.
Open the default installation path for the JDK:
C:\Program Files\Java
There should be a subdirectory like:
C:\Program Files\Java\jdk1.8.0_172
Note: one has only to put the path to the jdk without /bin in the end (as suggested on a lot of places). e.g. C:\Java\jdk1.8.0_172 and NOT C:\Java\jdk1.8.0_172\bin !
Set the JAVA_HOME Variable
Once you have the JDK installation path:
Right-click the My Computer icon on your desktop and select Properties.
Click the Advanced tab, then click the Environment Variables button.
Under System Variables, click New.
Enter the variable name as JAVA_HOME.
Enter the variable value as the installation path for the Java Development Kit.
Click OK.
Click Apply Changes.
Note: You might need to restart Windows
The complete article is here, on my blog: Setting JAVA_HOME Variable in Windows.

What worked for me was adding the %JAVA_HOME%\bin to the Path environment variable with the JAVA_HOME environment variable pointing to the jdk folder.

You have to first Install JDK in your system.
Set Java Home
JAVA_HOME = C:\Program Files\Java\jdk1.7.0 [Location of your JDK Installation Directory]
Once you have the JDK installation path:
Right-click the My Computer icon on
Select Properties.
Click the Advanced system setting tab on left side of your screen
Aadvance Popup is open.
Click on Environment Variables button.
Under System Variables, click New.
Enter the variable name as JAVA_HOME.
Enter the variable value as the installation path for the Java Development Kit.
Click OK.
Click Apply Changes.
Set JAVA Path under system variable
PATH= C:\Program Files\Java\jdk1.7.0; [Append Value with semi-colon]

In cmd (temporarily for that cmd window):
set JAVA_HOME="C:\\....\java\jdk1.x.y_zz"
echo %JAVA_HOME%
set PATH=%PATH%;%JAVA_HOME%\bin
echo %PATH%

You need to set it to C:\Sun\SDK\jdk (Assuming that is where the JDK is installed - It is not the default) - Do not put the \bin in C:\Sun\SDK\jdk\bin.
If your app only runs when you are logged in as the current user then put it in the user variables - If it needs to run for all users on your system then put it in System variables.
You might also need to add %JAVA_HOME%\bin to the path also (Also it depends on whether you run it from just the user or from all users, including System)

http://javahowto.blogspot.com/2006/05/javahome-vs-javahome.html
Control Panel > Java, Java tab, click the View button. In Runtime Parameters, put:
-Djava.home=YOUR_PATH_HERE
Or when you execute Java you can add that command line switch to the command:
java -Djava.home=PATH SomeJavaApp

One Image can fix this issue.
For More

For those who are still stumped with this problem (I tried all the above suggestions) --
If you're on a 64-bit version of Windows and you've installed the 32-bit JDK, besides adjusting PATH variables, you may need to adjust registry variables, too.
I was pulling my hair out, having correctly set my PATH variables -- still to no avail -- and then only finding "vacated" Java entries in my registry, seemingly a deadend of fixing the "misfiring" Java Runtime Environment.
By using Process Monitor to watch the program I was trying to get started, in order to sniff out where it was looking in the registry for Java (Runtime Environment), I triumphantly discovered that it's looking in the 32-bit version of registry entries, found in HKEY_LOCAL_MACHINE\SOFTWARE\**Wow6432Node**\JavaSoft\Java Runtime Environment.
Within that key, you should find subkeys of different Java versions installed (past and/or present). Click on the subkey of the latest version (my subkey is currently 1.7.0_25, for example). After clicking on that subkey, you'll see registry string values listed on the right, and particularly, JavaHome and RuntimeLib. You need to modify the values of those two values to reflect the both the current folder and jvm.dll file, respectively.
For example, in my case, the values were (previously) respectively set at C:\Program Files (x86)\Java\jre7 and C:\Program Files (x86)\Java\jre7\bin\client\jvm.dll which are nonexistent on my machine. I had to update these to the current folder and file of C:\Program Files (x86)\Java\jdk1.7.0_25\jre and C:\Program Files (x86)\Java\jdk1.7.0_25\jre\bin\client\jvm.dll.
Again, this will depend entirely on both what version of Java (JDK and/or JRE) you have installed -- 32 or 64-bit -- and what type of operating system you're on -- 32 or 64-bit. Just know that they're reflected in different locations within the registry (like the Wow6432Node for 32 bit applications, in my case with the 32-bit JDK installed on a 64-bit machine).
Now that I've updated those two registry values, my program runs flawlessly, with no more hiccups or complaints about a missing Java Runtime Environment (stemming from the registry).

This is the official solution for setting the Java environment from www.java.com - here.
There are solutions for Windows 7, Windows Vista, Windows XP, Linux/Solaris and other shells.
Example
Windows 7
Select Computer from the Start menu
Choose System Properties from the context menu
Click Advanced system settings -> Advanced tab
Click on Environment Variables, under System Variables, find PATH, and click on it.
In the Edit windows, modify PATH by adding the location of the class to the value for PATH. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value.
Reopen Command prompt window, and run your Java code.

Windows 7
Go to Control Panel\All Control Panel Items\User Accounts using Explorer (not Internet Explorer!)
or
click on the Start button
click on your picture
Change my environment variables
New...
(if you don't have enough permissions to add it in the System variables section, add it to the User variables section)
Add JAVA_HOME as Variable name and the JDK location as Variable value > OK
Test:
open a new console (cmd)
type set JAVA_HOME
expected output: JAVA_HOME=C:\Program Files\Java\jdk1.8.0_60

We need to make a distinction between the two environment variables that are discussed here interchangeably. One is the JAVA_HOME variable. The other is the Path variable. Any process that references the JAVA_HOME variable is looking for the search path to the JDK, not the JRE. The use of JAVA_HOME variable is not meant for the Java compiler itself. The compiler is aware of its own location. The variable is meant for other software to more easily locate the compiler. This variable is typically used by IDE software in order to compile and build applications from Java source code. By contrast, the Windows CMD interpreter, and many other first and third party software references the Path variable, not the JAVA_HOME variable.
Use case 1: Compiling from CMD
So for instance, if you are not using any IDE software, and you just want to be able to compile from the CMD, independent of your current working directory, then what you want is to set the Path variable correctly. In your case, you don't even need the JAVA_HOME variable. Because CMD is using Path, not JAVA_HOME to locate the Java compiler.
Use case 2: Compiling from IDE
However, if you are using some IDE software, then you have to look at the documentation first of all. It may require JAVA_HOME to be set, but it may also use another variable name for the same purpose. The de-facto standard over the years has been JAVA_HOME, but this may not always be the case.
Use case 3: Compiling from IDE and CMD
If in addition to the IDE software you also want to be able to compile from the CMD, independent of your current working directory, then in addition to the JAVA_HOME variable you may also need to append the JDK search path to the Path variable.
JAVA_HOME vs. Path
If your problem relates to compiling Java, then you want to check the JAVA_HOME variable, and Path (where applicable). If your problem relates to running Java applications, then you want to check your Path variable.
Path variable is used universally across all operating systems. Because it is defined by the system, and because it's the default variable that's used for locating the JRE, there is almost never any problem running Java applications. Especially not on Windows where the software installers usually set everything up for you. But if you are installing manually, the safest thing to do is perhaps to skip the JAVA_HOME variable altogether and just use the Path variable for everything, for both JDK and the JRE. Any recent version of an IDE software should be able to pick that up and use it.
Symlinks
Symbolic links may provide yet another way to reference the JDK search path by piggybacking one of the existing environment variables.
I am not sure about previous versions of Oracle/Sun JDK/JRE releases, but at least the installer for jdk1.8.0_74 appends the search path C:\ProgramData\Oracle\Java\javapath to the Path variable, and it puts it at the beginning of the string value. This directory contains symbolic links to the java.exe, javaw.exe and javaws.exe in the JRE directory.
So at least with the Java 8 JDK, and presumably the Java 8 JRE standalone, no environment variable configuration needs to be done for the JRE. As long as you use the installer package to set it up. There may be differences on your Windows installation however. Note that the Oracle JRE comes bundled with the JDK.
If you ever find that your Java JDK configuration is using the wrong version of the compiler, or it appears to be working by magic, without being explicitly defined so (without casting the spell), then you may have a symlink somewhere in your environment variables. So you may want to check for symlink.

goto Mycomputer(This PC) -> rightclick ->select properties -> Advanced system settings -> environment variables-> in system variables click "New" button and write JAVA_HOME in variable name and path C:\Program Files\Java\jdk1.8.0_131 were jdk is present in variable value-> click ok.
close and reopen the command prompt after setting JAVA_HOME. Sometimes changes does not reflect in the cmd opened before setting the JAVA_HOME.
you can also set JAVA_HOME through terminal itself:
SET JAVA_HOME="C:\Program Files (x86)\Java\jdk1.8.0_131"

In Eclipse: Window->Preferences->Java->Installed JREs
Use the search feature to make sure your latest Java installation is listed; then make sure it is the one that is checked. This should be a JDK not a JRE.

While adding your Java directory to your PATH variable, you might want to put it right at the beginning of it. I've had the problem, that putting the Java directory at the end of the PATH would not work. After checking, I've found java.exe in my Windows\System32 directory and it looks like the first one wins, when there are several files with the same name in your PATH...

Run Eclipse as Administrator.
That solved my problem. I'm still digging for the logic behind it.

if you have not restarted your computer after installing jdk just restart your computer.
if you want to make a portable java and set path before using java, just make a batch file i explained below.
if you want to run this batch file when your computer start just put your batch file shortcut in startup folder. In windows 7 startup folder is "C:\Users\user\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup"
make a batch file like this:
set Java_Home=C:\Program Files\Java\jdk1.8.0_11
set PATH=%PATH%;C:\Program Files\Java\jdk1.8.0_11\bin
note:
java_home and path are variables. you can make any variable as you wish.
for example set amir=good_boy and you can see amir by %amir% or you can see java_home by %java_home%

After hours of work around most of the solutions here, the problem was solved for me just by installing 32-bit JDK.

You may wanna look into Windows/System32 folder for the following files:
- java.exe
- javaw.exe
- javaws.exe
Because, the path variable is including these files, you can get a headache trying to figure out why the java -version or javac -version keeps pointing to the old JAVA_HOME: rename those files, take out the extension with an underscore, for instance. And then, you only will have to create the JAVA_HOME variable, add it to the path variable (e.g., %JAVA_HOME%) and append the "\bin" particle. This way you need to only change the JAVA_HOME variable pointing to different JRE or JDK and have multiple installations of java just by setting JAVA_HOME.
This also means that it is better to install Java manually, without an installer, so you are able to toy with it.

the Terminal of Android Studio can't work [duplicate]

I went to the Environment Variables in 'System' in the control panel and made two new variables, one for user variables and one for system variables. Both were named JAVA_HOME and both pointing to
C:\Sun\SDK\jdk\bin
But for some reason, I still get the below error when running a Java command...
BUILD FAILED
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:161: The following error occurred while executing this line:
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:141: The following error occurred while executing this line:
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish\setup.xml:137: Please set java.home to a JDK installation
Total time: 1 second
C:\Users\Derek\Desktop\eclipse\eclipse\glassfish>lib\ant\bin\ant -f setup.xml
Unable to locate tools.jar. Expected to find it in C:\Program Files\Java\jre6\lib\tools.jar
Buildfile: setup.xml
How can I fix this problem?

Find JDK Installation Directory
First you need to know the installation path for the Java Development Kit.
Open the default installation path for the JDK:
C:\Program Files\Java
There should be a subdirectory like:
C:\Program Files\Java\jdk1.8.0_172
Note: one has only to put the path to the jdk without /bin in the end (as suggested on a lot of places). e.g. C:\Java\jdk1.8.0_172 and NOT C:\Java\jdk1.8.0_172\bin !
Set the JAVA_HOME Variable
Once you have the JDK installation path:
Right-click the My Computer icon on your desktop and select Properties.
Click the Advanced tab, then click the Environment Variables button.
Under System Variables, click New.
Enter the variable name as JAVA_HOME.
Enter the variable value as the installation path for the Java Development Kit.
Click OK.
Click Apply Changes.
Note: You might need to restart Windows
The complete article is here, on my blog: Setting JAVA_HOME Variable in Windows.

What worked for me was adding the %JAVA_HOME%\bin to the Path environment variable with the JAVA_HOME environment variable pointing to the jdk folder.

You have to first Install JDK in your system.
Set Java Home
JAVA_HOME = C:\Program Files\Java\jdk1.7.0 [Location of your JDK Installation Directory]
Once you have the JDK installation path:
Right-click the My Computer icon on
Select Properties.
Click the Advanced system setting tab on left side of your screen
Aadvance Popup is open.
Click on Environment Variables button.
Under System Variables, click New.
Enter the variable name as JAVA_HOME.
Enter the variable value as the installation path for the Java Development Kit.
Click OK.
Click Apply Changes.
Set JAVA Path under system variable
PATH= C:\Program Files\Java\jdk1.7.0; [Append Value with semi-colon]

In cmd (temporarily for that cmd window):
set JAVA_HOME="C:\\....\java\jdk1.x.y_zz"
echo %JAVA_HOME%
set PATH=%PATH%;%JAVA_HOME%\bin
echo %PATH%

You need to set it to C:\Sun\SDK\jdk (Assuming that is where the JDK is installed - It is not the default) - Do not put the \bin in C:\Sun\SDK\jdk\bin.
If your app only runs when you are logged in as the current user then put it in the user variables - If it needs to run for all users on your system then put it in System variables.
You might also need to add %JAVA_HOME%\bin to the path also (Also it depends on whether you run it from just the user or from all users, including System)

http://javahowto.blogspot.com/2006/05/javahome-vs-javahome.html
Control Panel > Java, Java tab, click the View button. In Runtime Parameters, put:
-Djava.home=YOUR_PATH_HERE
Or when you execute Java you can add that command line switch to the command:
java -Djava.home=PATH SomeJavaApp

One Image can fix this issue.
For More

This is the official solution for setting the Java environment from www.java.com - here.
There are solutions for Windows 7, Windows Vista, Windows XP, Linux/Solaris and other shells.
Example
Windows 7
Select Computer from the Start menu
Choose System Properties from the context menu
Click Advanced system settings -> Advanced tab
Click on Environment Variables, under System Variables, find PATH, and click on it.
In the Edit windows, modify PATH by adding the location of the class to the value for PATH. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value.
Reopen Command prompt window, and run your Java code.

Windows 7
Go to Control Panel\All Control Panel Items\User Accounts using Explorer (not Internet Explorer!)
or
click on the Start button
click on your picture
Change my environment variables
New...
(if you don't have enough permissions to add it in the System variables section, add it to the User variables section)
Add JAVA_HOME as Variable name and the JDK location as Variable value > OK
Test:
open a new console (cmd)
type set JAVA_HOME
expected output: JAVA_HOME=C:\Program Files\Java\jdk1.8.0_60

goto Mycomputer(This PC) -> rightclick ->select properties -> Advanced system settings -> environment variables-> in system variables click "New" button and write JAVA_HOME in variable name and path C:\Program Files\Java\jdk1.8.0_131 were jdk is present in variable value-> click ok.
close and reopen the command prompt after setting JAVA_HOME. Sometimes changes does not reflect in the cmd opened before setting the JAVA_HOME.
you can also set JAVA_HOME through terminal itself:
SET JAVA_HOME="C:\Program Files (x86)\Java\jdk1.8.0_131"

In Eclipse: Window->Preferences->Java->Installed JREs
Use the search feature to make sure your latest Java installation is listed; then make sure it is the one that is checked. This should be a JDK not a JRE.

While adding your Java directory to your PATH variable, you might want to put it right at the beginning of it. I've had the problem, that putting the Java directory at the end of the PATH would not work. After checking, I've found java.exe in my Windows\System32 directory and it looks like the first one wins, when there are several files with the same name in your PATH...

Run Eclipse as Administrator.
That solved my problem. I'm still digging for the logic behind it.

if you have not restarted your computer after installing jdk just restart your computer.
if you want to make a portable java and set path before using java, just make a batch file i explained below.
if you want to run this batch file when your computer start just put your batch file shortcut in startup folder. In windows 7 startup folder is "C:\Users\user\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup"
make a batch file like this:
set Java_Home=C:\Program Files\Java\jdk1.8.0_11
set PATH=%PATH%;C:\Program Files\Java\jdk1.8.0_11\bin
note:
java_home and path are variables. you can make any variable as you wish.
for example set amir=good_boy and you can see amir by %amir% or you can see java_home by %java_home%

After hours of work around most of the solutions here, the problem was solved for me just by installing 32-bit JDK.

You may wanna look into Windows/System32 folder for the following files:
- java.exe
- javaw.exe
- javaws.exe
Because, the path variable is including these files, you can get a headache trying to figure out why the java -version or javac -version keeps pointing to the old JAVA_HOME: rename those files, take out the extension with an underscore, for instance. And then, you only will have to create the JAVA_HOME variable, add it to the path variable (e.g., %JAVA_HOME%) and append the "\bin" particle. This way you need to only change the JAVA_HOME variable pointing to different JRE or JDK and have multiple installations of java just by setting JAVA_HOME.
This also means that it is better to install Java manually, without an installer, so you are able to toy with it.

How important is setting environment variables in Java?

I am writing a blog where I have explain my students how to install Java, but I'm wondering why should expose them to this complicated part of Java installation. When I used Java before, I used right out of the box with my IDE. But all the tutorials I see mention configuration of these environment variables.
Maybe my PATH variables were set from previous installations, however I don't remember doing it.
Can anyone please advise if environment variable setting can be left to the IDEs or has to be done manually?

Java does not need any environment variables to be set.
However, setting some environment variables makes some things easier.
PATH If the jre/bin folder is on the path, you don't have to qualify to run the java command. If the jdk/bin folder is on the path, you don't have to qualify to run the java and javac commands. As well as some other commands provided by Java.
JAVA_HOME Used by many Java programs and installers to find Java.
When using an IDE, it can usually find / prompt for Java installations, so it doesn't need any environment variables. The IDE won't set them either.

As mentioned above, JAVA_HOME Used by many Java programs and installers to locate Java. for instance, Tomcat requires the environment variable JAVA_HOME to be set to the JDK installed directory.
To check if JAVA_HOME is already set, start a terminal and issue:
echo $JAVA_HOME
JAVA_HOME is to be set to the JDK installed directory. You need to find your JDK installed directory.
[TODO] find macOS and Ubuntu JDK installed directory.
Add the the following line at the end of "~/.bashrc" (or "~/.login"). Take note that filename beginning with dot (.) is hidden by default.
[TODO] How to un-hide for macOS/Ubuntu.
export JAVA_HOME=/path/to/JDK-installed-directory
// Verify the new setting
echo $JAVA_HOME

I installed Java and then installed Eclipse, and you know what, it worked fine, however for one of my colleagues it was giving a "warning" regarding not being able to find Java, and error was clearly showing it needs environment variables because it wasn't able to find the path to Java, like Java wasn't installed, while it was installed there.

Ant and Eclipse

Hi I am a beginner java programmer and recently I've started reading Thinking in Java 4th edition to consolidate my knoledge of java after I read Head first Java.Problem is that this book has it's own library and I can't seem to make it work in eclipse even after I did everything it said on the website guide.I instaled ant acordinly with this video guide http://www.youtube.com/watch?v=XJmndRfb1TU and i'm getting this error:
"Unable to locate tools.jar.Expected to find it in C:\Program files\Java\jre7\lib\tools.jar
Buildfile:C:\TIJ4\code\build.xml
build:
BUILD FAILED
C:\TIJ4\code\build.xml:59:J2SE5 required
Total time:0 seconds
I tried reinstaling JDK witch was suggested on a forum but it still dident work so I don't really know what to do.
Can anyone tell me how can I solve this problem? Also, more importantly, can't this be done with Eclipse alone without installing Ant(I've only used eclipse for code writing and compiling so I'm not very familiar with it)Thant you.

You are using a JRE instead of a JDK. Install a JDK and point your PATH and JAVA_HOME variables to the JDK home, not to the JRE home.
I see that Ant is using the Java Home from the JRE, e.g. C:\Program files\Java\jre7\
But it should be C:\Program files\Java\jdk1.7.0\ or similar.
Check your system's environment variables (e.g. press Windows-Key and Pause together, then select Extended Settings > Environment Variables. Check that JAVA_HOME is set to the JDK installation path and that in the PATH variables, the folder of the JDK comes before the folder of the JRE (or remove/replace the JRE path altogether with the one from the JDK).
Ant needs to find the JDK first in the PATH.

Install the JDK, latest version, and check the environment variable JAVA_HOME.
If it is not found, create it and set it to C:\Program Files\Java\jdk1.7.0 ...

tools.jar contains the java compiler, and only comes with the Java Development Kit (JDK). Your error message point to the Java Runtime (JRE).
From Eclipse, you set that from Window/Preferences/Java/Installed JREs. This is equivalent to, and will override, the alternative way of setting it via Windows environment variables.

I tried installing the JDK - jdk1.7.0_09
and did whatever was needful in the Environment Variables section
but i still was getting this error
"Unable to locate tools.jar. Expected to find it in C:\Program Files\Java\jre7\li
b\tools.jar
Buildfile: build.xml does not exist!
Build failed"
Tools.jar file did not really exists in this path, instead i found it in C:\Program Files\Java\jdk1.7.0_09\lib
so i simply copied this tools.jar file and placed it under C:\Program Files\Java\jre7\li
b\
and it worked - (not sure if that was the right way)
Now when i typed in the cmd prompt "ant" it gave me the below error :
Buildfile: build.xml does not exist!
Build failed
On investigating it further i found that if you get the above error it means that ant is installed successfully
http://ant.apache.org/manual/install.html#getBinary - Check Installation

what ivantrox86 said is true, but you need to do it in all the build.xml files, and there are like 20 of them. so go to each and every folder in the c:\tij4\code directory and find every build.xml file, and change the second argument (arg2) to 1.5, instead of the default value (${ant.java.version}). works 100%

This can happen with ant if JAVA_HOME is set incorrectly - it seems to try to guess what the value should be and comes up with the jre7 address. In my case setting JAVA_HOME to C:\Progra~1\Java\jdk1.7.0_45 fixed the problem. Of course the address will vary depending on where your jdk is installed.

please search and change this line in all files.:
<equals arg1="1.5" arg2="${ant.java.version}"/>
for
<equals arg1="1.5" arg2="1.5"/>

Why does java -version return an old version?

OS: Windows XP
I am using yuicompressor-2.4.2 to compress some CSS before uploading to my server.
But when I run it, the following exception appears:
Exception in thread "main" java.lang.UnsupportedClassVersionError:
com/yahoo/platform/yui/compressor/Bootstrap (Unsupported major.minor version 48.0)
So I think it's because of the JRE.
I typed in the command:
cmd: java -version
And it says:
java version "1.3.1_01"
But it should say 1.6.0_16, since I have installed the latest version.
What should I do to make Java use the latest version instead of the old one?

Set the environment variable JAVA_HOME pointing to the directory where you have jdk 1.6.0
set JAVA_HOME=your_path_to_jdk1.6
set PATH=%JAVA_HOME%/bin;.;..;%PATH%
That's from a command window. Also you can do it from "My PC > Properties > Advanced > Environment variables"

Go to the system32 directory C:\Windows\System32 and delete following 3 files
java.exe
javaw.exe
javaws.exe
Now create a JAVA_HOME environment variable with value={root path of your jdk installation} and add the path till bin folder of your jdk in the PATH environment variable.
Open a fresh command prompt and run java -version to confirm the change

If you are using windows 7/10 go to command prompt and type
where java
Delete all the symbolic link shows below other than your actual installation directory.
Even if correctly added all the environment variables still sometime you can get wrong versions especially when you have multiple version installed in your system and want to switch between them.

On Windows, the JRE installs a java executable in the Windows directory, which should be the first java in your path. This is just a wrapper that looks in the Windows Registry to find the Java home directory (should be "%SystemDrive%\Program Files\Java\jre6" for Java 6) and runs using the libraries there.
Run %SystemRoot%\system32\java -version and see what you get. If that is Java 6, you have entries in your path before %SystemRoot%\system32 (which really should be first). Either fix your %PATH% variable, or you'll have to be explicit whenever you want to run this version of Java.
If running that instance of java doesn't report Java 6, its not installed (correctly). Uninstall and try installing again.
If you are having trouble because of the PATH, it is because you or some software you installed monkeyed with it; I recommend using the default which is to have system32 first. Everything works fine if the defaults are used.
Also, %JAVA_HOME% is not used by the JRE itself at all. Some common Java applications like tomcat and ant honor the %JAVA_HOME% setting, so perhaps yuicompressor does too. But this is a de facto convention, not a standard.

after where java in Command prompt
for example
where java
C:\Program Files\Common Files\Oracle\Java\javapath
C:\Program Files\Java\jdk-11.0.10\bin\java.exe
delete C:\Program Files\Common Files\Oracle folder
then close all terminals and write java -version in the terminal. it will show the right version
worked for me

You should modify your PATH environment variable:
My PC > Right click > properties > Advanced > Environment variables
And modify "Path"
Append at the end the path to your 1.6 installation:
;C:\jdk1.6.xxx\bin
and remove the previous one if present.

Add %JAVA_HOME%/bin to your PATH environment variable where JAVA_HOME is set to your JRE6u16 directory

I had the same problem. In System Properties > Environment Variables > System Variables > PATH make sure there is no other path associated with Java. To make sure, type in and check Java paths.
where java
Re-open Command Prompt and type java -version again. I hope this helps.

first by the following command, you should be aware of .exe file which runs when you type java in the command prompt
where java
C:\Program Files\Common Files\Oracle\Java\javapath
C:\Program Files\Java\jdk-11.0.10\bin\java.exe
as you see above , cmd first reads java from
C:\Program Files\Common Files\Oracle\Java\javapath
so go to the path above and remove java files .
then it should work fine

You should check your PATH environment variable. It is possible that some application you have installed has put its version of the jre in front of yours in the path.

It looks like the older Java version is still on the system PATH environment variable (where the OS looks for commands) or JAVA_HOME (where yuicompressor may look for the java executable)
How those variables are changed depends on your operating system.

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