Unable to locate tools.jar

I am building a project in Java.

I have this error:

Unable to locate tools.jar. Expected to find it in C:\Program Files\Java\jre6\lib\tools.jar

I have installed a JDK and the folder: C:\Program Files\Java\jre6\lib is in my system but the file tools.jar is not there.

Yes, you’ve downloaded and installed the Java Runtime Environment (JRE) instead of the Java Development Kit (JDK). The latter has the tools.jar, java.exe, javac.exe, etc.