Commons Lang、ClassUtils.getPackageName()

import org.apache.commons.lang.ClassUtils;
import java.util.*;

public class C2009082000 {
    public static void main(String[] args) {
        System.out.println(ClassUtils.getPackageName(String.class));
        System.out.println(ClassUtils.getPackageName(Integer.class));
        System.out.println(ClassUtils.getPackageName(LinkedList.class));

        System.out.println(ClassUtils.getPackageName("java.lang.String"));
        System.out.println(ClassUtils.getPackageName("java.lang.Integer"));
        System.out.println(ClassUtils.getPackageName("java.util.LinkedList"));
    }
}

で、

java.lang
java.lang
java.util
java.lang
java.lang
java.util