JavaPPuzzler :)

_Puzzler on JavaP

Given these 5 classes, could you guess :
(1) What is the number of total generated classes ?
(2) and (3) : Can you guess what are superclasses and implemented interfaces for every generated classes in (1) ?

Answers are here : https://gist.github.com/1771083

com.puzzlers.a.SimpleEnum.java

package com.puzzlers.a;

import java.io.Serializable;

public enum SimpleEnum implements Serializable {
    VALUE;
}

com.puzzlers.b.SimpleAnonymousEnum.java

package com.puzzlers.b;

import java.io.Serializable;

public enum SimpleAnonymousEnum implements Serializable {
    VALUE(){};
}

com.puzzlers.c.ClassWithNestedEnum.java

package com.puzzlers.c;

import java.io.Serializable;

public class ClassWithNestedEnum implements Serializable {
    public static enum NestedEnum implements Serializable {
        VALUE();
    }
}

com.puzzlers.d.ClassWithNestedAnonymousEnum.java

package com.puzzlers.d;

import java.io.Serializable;

public class ClassWithNestedAnonymousEnum {
    public static enum NestedAnonymousEnum implements Serializable {
        VALUE(){};
    }
}

com.puzzlers.JavaPPuzzler.java

package com.puzzlers;

import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.util.ClassUtils;
import org.springframework.util.SystemPropertyUtils;

import java.io.IOException;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class JavaPPuzzler implements Serializable {
    public static void main(String[] args) throws ClassNotFoundException, IOException {
        List<Class> classesInPuzzlerPkg = findTypesInPackage("com.puzzlers");

        // Guessing how many classes are there in package com.puzzlers ?
        System.out.println(classesInPuzzlerPkg.size()); // Answer is in (1)

        System.out.println(String.format("%n%n%n"));

        // Now, displaying every superclass for every retrieved classes
        for(Class clazz : classesInPuzzlerPkg){
            System.out.println(clazz.getName() + " has superclass : " + clazz.getSuperclass());

            // and compare it with what javap displays ... :) (2)
        }

        System.out.println(String.format("%n%n%n"));
        
        for(Class clazz : classesInPuzzlerPkg){
            System.out.println(clazz.getName() + " implements Serializable ? " + Serializable.class.isAssignableFrom(clazz));

            // and compare it with what javap displays ... :) (3)
        }
    }

    /**
     * Retrieving types in given package... 'works fine, puzzler doesn't reside here ;)
     */
    private static List<Class> findTypesInPackage(String basePackage) throws IOException, ClassNotFoundException {
        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(resourcePatternResolver);

        List<Class> candidates = new ArrayList<Class>();
        String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
                resolveBasePackage(basePackage) + "/" + "**/*.class";
        Resource[] resources = resourcePatternResolver.getResources(packageSearchPath);
        for (Resource resource : resources) {
            if (resource.isReadable()) {
                MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(resource);
                //if (isCandidate(metadataReader)) {
                    candidates.add(Class.forName(metadataReader.getClassMetadata().getClassName()));
                //}
            }
        }
        return candidates;
    }
    
    private static String resolveBasePackage(String basePackage) {
        return ClassUtils.convertClassNameToResourcePath(SystemPropertyUtils.resolvePlaceholders(basePackage));
    }
    
}