Collections 和Collection的区别

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1、java.util.Collection 是一个集合接口。它提供了对集合对象进行基本操作的通用接口方法。Collection接口在Java 类库中有很多具体的实现。Collection接口的意义是为各种具体的集合提供了最大化的统一操作方式。

Collection
├List
│├LinkedList
│├ArrayList
│└Vector
│　└Stack
└Set

2、java.util.Collections 是一个包装类。它包含有各种有关集合操作的静态多态方法。此类不能实例化，就像一个工具类，服务于Java的Collection框架。

package ch3;import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.Iterator;import java.util.List;public class CollectionsText {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stub   List list = new ArrayList();   Student s1 = new Student(21,"zhang");   Student s2 = new Student(25,"zhao");   Student s3 = new Student(11,"li");   Student s4 = new Student(29,"wang");   Student s5= new Student(32,"zhang");   list.add(s1);   list.add(s2);   list.add(s3);   list.add(s4);   list.add(s5);      System.out.println("初始化list:");   printView(list);         Collections.shuffle(list);   System.out.println("混淆后list内容：");   printView(list);      Collections.sort(list);   System.out.println("排序后：");   printView(list);         Collections.reverse(list);   System.out.println("逆序后：");   printView(list);         List newlist = new ArrayList(Arrays.asList(new Object[list.size()]));   Collections.copy(newlist, list);   System.out.println("复制list内容：");   printView(newlist);      }private static void printView(List list) {// TODO Auto-generated method stubIterator in = list.iterator();while(in.hasNext()){System.out.print(in.next()+"\t");}System.out.println();}}