How to find the location of java class files at runtime?

Question

Does anyonw have an idea how to get the file name of a java class given the binary name?
I mean how can I get the file name for my class myPackage.myClass?
I am looking for a function which takes "myPackage.myClass" as input and returns
"c:\\javaprojects\\myPackage\\myClass.class".
I tried to do it with the LassLoader class but it did not work. Does anyone have an idea if the Java core API already has a function which does that?
Thanks, Bernhard

Answer 1

Hi ,
It is a simple SAMPLE code , you think and build a logics to handle all classes.
Try this sample, It doesn't handle the inner classes you put logic to handle the logics for inner classes.
The inner class format is it contains the character $ in the File location but inside the code you put "." instedad of "$" you to find out or put trials.
package pkg1;
import java.io.* ;
import java.util.* ;
import java.util.zip.* ;
public class ClsB {
     private static Vector clsPaths ;
     public static Vector getPaths() {
          if( clsPaths == null ) {
               String paths = System.getProperty( "java.class.path" ) ;
               // In linux or solarise use the following
               // StringTokenizer st = new StringTokenizer( paths , ":\n" ) ;
               StringTokenizer st = new StringTokenizer( paths , ";\n" ) ;
               clsPaths = new Vector() ;
               while( st.hasMoreTokens() ) {
                    String path = st.nextToken() ;
                    File f = new File( path ) ;
                    if( f.exists() ) {
                         try {
                              f = f.getCanonicalFile() ;
                              clsPaths.add( f ) ;
                         }catch( IOException ioe ) { }
          return clsPaths ;
     public static String findClassPath( String fullClassName ) {
          Vector v = getPaths() ;
          for( int i = 0 ; i < v.size() ; i++ ) {
               File f = ( File ) v.get( i ) ;
               String path = findIn( f , fullClassName ) ;
               if( path != null )
                    return path ;
          return null ;
     static boolean isJar( File jar ) {
          if( jar.isDirectory() )
               return false ;
          try {
               ZipFile zf = new ZipFile( jar ) ;
               return true ;
          } catch ( ZipException ze ) {
               // It is not a jar file
               // you handle this
          } catch ( IOException ioe ) {
               ioe.printStackTrace() ;
          return false ;
     static String findIn( File dirOrJar , String clsName ) {
          if( isJar( dirOrJar ) ) {
               // It is something different because the class inside the jar file
               // Simply I return the jar file location and the entry name ,
               // but you put action what you want
               if( isInsideJar( dirOrJar , clsName ) ) {
                    // All archieve file using the path separator is '/'
                    return dirOrJar.getPath() + "!" + clsName.replace( '.' , '/' ) + ".class" ;
          } else {
               File f = new File( dirOrJar , clsName.replace( '.' , File.separatorChar ) + ".class" ) ;
               if( f.exists() ) {
                    return f.getPath() ;
          return null ;
     static boolean isInsideJar( File jar , String clsName ) {
          try {
               ZipFile zf = new ZipFile( jar ) ;
               // All archieve file using the path separator is '/'
               ZipEntry ze = zf.getEntry( clsName.replace( '.' , '/' ) + ".class" );
               return ( ze != null ) ;
          } catch ( ZipException ze ) {
               ze.printStackTrace() ;
          } catch ( IOException ioe ) {
               ioe.printStackTrace() ;
          return false ;
     public static void main(String[] args) {
          System.out.println( findClassPath( "pkg1.ClsB" ) );
          System.out.println( findClassPath( "pkg1.pkg2.ClsA" ) );
}