Inspecting a package

Posted on 2002-04-10
Last Modified: 2010-03-31

I need to inspect all the classes of a certain package (for example java.util).
I was looking for a piece of code like
Classes [] classes = new Package("java.util").getClasses()

but this method does not exist.
Anyone knows how can i do it?
Question by:ebuchner
LVL 92

Expert Comment

ID: 6932662
No easy way to do that. The class loader only loads classes on demand, so until a class is needed it knows nothing about it.
LVL 35

Expert Comment

ID: 6932773
 Objects is right, it is not easy to do it. What I can think off the top of my head is to write your customized class loader that goes through a given subdirectory (package) recursively and loads all the classes. Then you can use reflection to get the properties and methods of the classes.

 Hope it helps.

Accepted Solution

Igor Bazarny earned 200 total points
ID: 6933338

If you are using default classloader, you can use java.class.path, sun.boot.class.path and java.ext.dirs system properties and,* classes to list .class files there.

Something like that (just an idea):

String package = "java.util"
String packageDir = package.replace('.',File.separatorChar);
String packageInZip = package.replace('.', '/')+"/";
ArrayList classes = new ArrayList();

StringBuffer buffer = new StringBuffer(System.getProperty("sun.boot.class.path"));

StringTokenizer extTokens = new StringTokenizer(System.getProperty("java.ext.dirs"), File.pathSeparator);
    File root = new File(extTokens.nextToken());
    File[] list = root.list();
    for(int i=0; i<list.length; ++i){
        if( list[i].getName().endsWith(".jar") ){
StringTokenizer pathTokens = new StringTokenizer(buffer.toString(), File.pathSeparator);

    File entry = new File(pathTokens.nextElement());
    if( entry.isDirectory() ){
        File dir = new File(entry,packageDir);
        if( dir.isDirectory() ){
            String[] list = dir.list();
            for( int i=0; i<list.length(); ++i){
                if( list[i].endsWith(".class") ){
        ZipFile zip = new ZipFile(entry);
        Enumeration zipEntries = zip.entries();
            String current = ((ZipEntry)entries.nextElement()).getName();
                String relative = current.substring(packageinZip.length());
                if( relative.indexOf("/") < 0 && relative.endsWith(".class")){

Igor Bazarny,
Brianbench MVP for Java 1


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