java---Collections

/*
 * 操作Collection以及Map的工具类：Collections
 * 面试题：区分Collection和Collections
 * 
 */
public class TestCollections {


@Test
public void test(){
List list = new ArrayList();
list.add(123);
list.add(456);
list.add(12);
list.add(78);
list.add(78);
System.out.println(list);
Collections.reverse(list);
System.out.println(list);

Collections.shuffle(list);
System.out.println(list);

Collections.sort(list);
System.out.println(list);
Collections.reverse(list);
System.out.println(list);

Collections.swap(list,0,2);//将指定的list集合中的两个元素位置互换
System.out.println(list);


}
@Test
public void test2(){
List list = new ArrayList();
list.add(123);
list.add(456);
list.add(12);
list.add(78);
list.add(78);

Object obj = Collections.max(list);
System.out.println(obj);

int count = Collections.frequency(list, 4567);
System.out.println(count);

//实现List的复制
//List list1 = new ArrayList();//错误的实现方式
List list1 = Arrays.asList(new Object[list.size()]);
Collections.copy(list1, list);
System.out.println(list1);

//通过如下的方法保证list的线程安全性
List list2 = Collections.synchronizedList(list);
System.out.println(list2);

}