類
Object
String
Date
Thread
Math
Integer
Long
File
(java.lang.Thread
Thread類的定義：public class Thread extends Object implements Runnable
)
===========================
包
java.lang.*;
java.io.*;
java.util.*;
java.sql.*;
java.math.*;
=======================
接口:
Comparable
Collection
Serializable
Map
List
Runnable(java.lang.Runnable 該接口的定義public interface Runnable)
Java集合框架：
接口：Collection、List、Set、Map、Iterator
類：Collections、ArrayList、HashMap