@Test

    public void test(){

        //contains()

        Collection coll = new ArrayList();

        coll.add(123);

        coll.add(456);

        coll.add(new String("Tom"));

        coll.add(false);

        Person p = new Person("jerry", 23);

        coll.add(p);

        coll.add(new Person("twq", 23));

        //1.contains（Object obj):判断当前集合中是否包含obj

        //我们在判断时会调用obj对象所在类的equals()方法

        boolean contains = coll.contains(123);

        System.out.println(contains);

        System.out.println(coll.contains(new String("Tom")));//判断的是内容而不是地址

        System.out.println(coll.contains(p));

        System.out.println(coll.contains(new Person("twq", 23)));

        System.out.println("===================");

        //2.containsAll(Collection call1):判断形参coll1中的所有元素是否都存在与当前集合中

        Collection coll1 = Arrays.asList(123,456);

        System.out.println(coll.containsAll(coll1));//判断coll中是否包含coll1

        System.out.println("===================");

        //3.remove(Object obj)：从当前集合中移除obj元素

        coll.remove(1234);

        System.out.println(coll);

        coll.remove(new Person("twq", 23));

        System.out.println(coll);

        System.out.println("===================");

        //4.removeAll(Collection coll1)：从当前集合中移除coll1中的所有的元素

        Collection coll2 = Arrays.asList(123,456);

        coll.removeAll(coll2);

        System.out.println(coll);

        System.out.println("===================");

        //5.retainAll(collection coll1) 交集：获取当前集合和coll1集合的交集

        Collection coll3 = Arrays.asList(false,"Tom");

        coll.retainAll(coll3);

        System.out.println(coll);

        System.out.println("===================");

        //6.equals(Object obj):要想返回true需要判断当前集合和形参集合的元素都相同

        Collection coll4 = new ArrayList();

        coll4.add(123);

        coll4.add(456);

        coll4.add(new String("Tom"));

        coll4.add(false);

        Collection coll5 = new ArrayList();

        coll5.add(123);

        coll5.add(456);

        coll5.add(new String("Tom"));

        coll5.add(false);

        System.out.println(coll4.equals(coll5));

        System.out.println("==================");

        //7.hashCode():返回当前对象的哈希值

        System.out.println(coll.hashCode());

        System.out.println("==================");

        //8.集合--->数组的转换：toArray()

        Object[] arr = coll.toArray();

        for (int i = 0; i < arr.length; i++) {

            System.out.println(arr[i]);

        }

        System.out.println("==================");

        //拓展：数组--->集合:调用Arrays类的静态方法asList()

        List<String> list = Arrays.asList(new String[]{"AA", "DD", "CC"});

        System.out.println(list);

        List<int[]> ints = Arrays.asList(new int[]{123, 456});

        System.out.println(ints.size());//虽然有两个元素，但是会默认为一个元素

        List ints1 = Arrays.asList(new Integer[]{123, 456});

        System.out.println(ints1.size());//这里可以正常输出

        System.out.println("==================");

    }

public void test1(){

    //iterator():返回

        Collection coll = new ArrayList();

        coll.add(123);

        coll.add(456);

        coll.add(new String("Tom"));

        coll.add(false);

        Iterator iterator = coll.iterator();

        while(iterator.hasNext()){//判断集合中是否还有元素

            System.out.println(iterator.next());

        }

    }

@Test

    public void test2(){

        Collection coll = new ArrayList();

        coll.add(123);

        coll.add(456);

        coll.add(new String("Tom"));

        coll.add(false);

        Iterator iterator = coll.iterator();

        while(iterator.hasNext()){

            Object obj = iterator.next();

            if(obj.equals("Tom")){

                iterator.remove();

            }

        }

        //这里必须重新定义一个迭代器变量，之前的迭代器变量已经指向了集合的末尾

        //新定义的迭代器变量指针默认指向集合的初始位置

        Iterator iterator1 = coll.iterator();

        while(iterator1.hasNext()){//判断集合中是否还有元素

            System.out.println(iterator1.next());

        }

    }