how to compile java file from different root directory

[s sivaraman]

HI,

i'd like to know how to compile a java file from different root directory.

i tried -classpath option but it doesn't seem to be working .

help me out.

thank you.

[Jeanne Boyarsky]

You just type javac and then the path to the file. For example,

javac /usr/my/file/that/is/located/elsewhere/com/coderanch/MyClass.java

This will produce the file /usr/my/file/that/is/located/elsewhere/com/coderanch/MyClass.class

[A.J. Côté]

Jeanne Boyarsky wrote:You just type javac and then the path to the file. For example,

javac /usr/my/file/that/is/located/elsewhere/com/coderanch/MyClass.java

This will produce the file /usr/my/file/that/is/located/elsewhere/com/coderanch/MyClass.class

She/he will need to set the classpath to the all the root directories otherwise MyClass.java wouldn't find the files (classes) it needs in the other directories.

What I usually do is this:

cd /usr/my/file/that/is/located/elsewhere

javac -classpath RootDir1:RootDir2:RootDir3:jarfilepath1:jarfilepath2:$CLASSPATH com/coderanch/MyClass.java

on windows, it should look like:

javac -classpath RootDir1;RootDir2;RootDir3;jarfilepath1;jarfilepath2;%CLASSPATH% com/coderanch/MyClass.java


If I remember correctly javac will recursively compile the files it needs to compile com/coderanch/MyClass as well in the other root folders.

[A.J. Côté]

I sometimes use scripts to set the classpath, basically:

setclasspath.sh
CLASSPATH=RootDir1:RootDir2:RootDir3:jarfilepath1:jarfilepath2:$CLASSPATH
export CLASSPATH

Then:
. .setclasspath #Notice the dot so CLASSPATH is applied to this shell
javac com/coderanch/MyClass.java

[Roel De Nijs]

s sivaraman wrote:i'd like to know how to compile a java file from different root directory.

i tried -classpath option but it doesn't seem to be working .

Let's take your source code file from one of your other topics

package com.pack;
class Sample {
  int i =99;
  public static void main(String [] args) {
    System.out.println("number = "+ new Sample().i);
  } }

Let's assume the source code file is located in the directory D:\ocajp\src\com\pack (as you can see I'm working on a Windows machine).

Now I can compile this source code file from the root directory D:\ usingD:\>javac ocajp/src/com/pack/Sample.javaAfter executing this command a Sample.class file is created in the directory D:\ocajp\src\com\pack. Now if you want to execute this .class file, you'll need to set the classpath to the appropriate directoryD:\>java -cp ocajp/src com.pack.Sample number = 99If you use a wrong directory in the classpath, the JVM won't be able to find your .class file and you'll get an appropriate error messageD:\>java -cp ocajp/wrong com.pack.Sample Error: Could not find or load main class com.pack.Sample

Now if you want to seperate your source code files from the generated .class files (which is considered to be a good practice), you can use the option -d of the javac command. So if we want to have the .class files being generated in the directory D:\ocajp\classes, you'll need to execute this commandD:\>javac -d ocajp/classes ocajp/src/com/pack/Sample.java javac: directory not found: ocajp/classes Usage: javac <options> <source files> use -help for a list of possible optionsAs you can see from this error message, the destination directory (in this example: D:\ocajp\classes) must exist! It's not created by the javac command. So after I have created the directory D:\ocajp\classes manually, I can run the previous command againD:\>javac -d ocajp/classes ocajp/src/com/pack/Sample.javaIt finishes without an error message and a Sample.class file is created in the directory D:\ocajp\classes\com\pack. Now if you want to execute this .class file, you'll need to set the classpath to the appropriate directoryD:\>java -cp ocajp/classes com.pack.Sample number = 99

Hope it helps!
Kind regards,
Roel