How import statements are included

[gpr]

Hi Friends
I am new to Java. I have a simple program wherein I am try to use some regex functions and it works fine. But, I am not able to understand how the import statement works.

My program has the following import statement:

import java.util.regex.*;

And this regex is inside a jar file which is located in C:\Program Files\Java\jdk1.6.0_07\jre\lib\rt.jar. My CLASSPATH variable is not set and is empty.

My question is: When I run the java program, how is it able to find out that my regex is inside rt.jar which is in so and so path since we dont have anything pointing to the location?

[rp181]

May be the IDE your using is pointing to that JAR file, or there is another one your are unaware of. Fairly sure that path is also the default (not sure, on Linux myself).

[liyuyu_852000]

yes ,rp181,I think you are right,
the IDE has contain the jar

[Junky]

My CLASSPATH variable is not set and is empty.

Check your JAVA_HOME environment variable.

[Tolls]

rt.jar is the basic runtime jar, containing all the standard java classes.
If you can run java programs then that jar file is accessible by the JVM.

[masijade]

rt.jar, as well as a large number of additional jars are on the bootstrap classpath which is based upon the directory in which the executing java command resides (unless you change it on the command line), and many other jars (a directoriey actually) are included as part of the "extension dirs" property which is also predetermined, and configurable, in the same manner.

Edit: There is also a bootstrap extension property, but that, normally, is empty.

[gpr]

Thanks a lot masijade. Understood the bootstrap classpath now.