Buddy
public class Buddy {

	private String qqId;
	private String qqName;
	private String impresa;
	
	public Buddy(String qqId, String name, String impresa){
		this.setImpresa(impresa);
		this.setQqId(qqId);
		this.setQqName(name);
	}
	
	public String getQqId() {
		return qqId;
	}
	public void setQqId(String qqId) {
		this.qqId = qqId;
	}
	public String getQqName() {
		return qqName;
	}
	public void setQqName(String qqName) {
		this.qqName = qqName;
	}
	public String getImpresa() {
		return impresa;
	}
	public void setImpresa(String impresa) {
		this.impresa = impresa;
	}

}

Group
import java.util.ArrayList;
import java.util.List;

public class Group {
	private String id;
	private String groupName;
	private List<Buddy> buddyList;
	
	public Group(String id,String groupName){
		this.setGroupName(groupName);
		this.setId(id);
		this.setBuddyList(new ArrayList<Buddy>());
	}
	public void addBuddy(Buddy buddy){
		
		this.buddyList.add(buddy);
	}
	
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getGroupName() {
		return groupName;
	}
	public void setGroupName(String groupName) {
		this.groupName = groupName;
	}
	public List<Buddy> getBuddyList() {
		return buddyList;
	}
	public void setBuddyList(List<Buddy> buddyList) {
		this.buddyList = buddyList;
	}
}

TestGroup
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class TestGroup {public static void main(String[] args) {
    
	List<Group> gList = new ArrayList<Group>();
	
	Group g1 = new Group("111","同學");		
	Group g2 = new Group("222","朋友");
	Group g3 = new Group("333","同事");
	gList.add(g1);
	gList.add(g2);
	gList.add(g3);
	
	
	Buddy hans = new Buddy("01","hans","I am good");
	Buddy rose = new Buddy("02","rose","I am bad");
	Buddy bruce = new Buddy("03","bruce","I am man");
	
	g1.addBuddy(hans);
	g1.addBuddy(rose);
	
	g2.addBuddy(bruce);
	g3.addBuddy(hans);
	
	
	Iterator<Group> git = gList.iterator();//遍歷組
	while(git.hasNext()){
		Group p = git.next();
		System.out.println("-"+p.getGroupName());
	    List<Buddy> bList = 	p.getBuddyList();
	    Iterator<Buddy> bit = bList.iterator();//遍歷組中的好友
	    while(bit.hasNext()){
	    	System.out.println("   |--"+bit.next().getQqName());
	    }
	}		
}}