6.2.2、Collection接口方法

public class CollectionTest {
    @Test
    public void test1(){
        Collection coll = new ArrayList();
        //add(Object e)将元素e添加到集合coll中
        coll.add("AA");
        coll.add("BB");
        coll.add("123");//自动装箱
        coll.add(new Date());
        //size():获取添加的元素的个数
        System.out.println(coll.size());//4
        //addAll(Collection coll1)：将coll1集合中的元素添加到当前的集合中
        Collection coll1 = new ArrayList();
        coll1.add(456);
        coll1.add("CC");
        coll.addAll(coll1);
        System.out.println(coll.size());//6
        System.out.println(coll);
        //clear():清空集合元素
        coll1.clear();
        //isEmpty()：判断当前集合是否为空
        System.out.println(coll1.isEmpty());//false
    }
}

public class CollectionTest {
    @Test
    public void test1() {
        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new String("Tom"));
        coll.add(false);
        coll.add(new Person("jerry", 20));
        //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();
        boolean contains = coll.contains(123);
        System.out.println(contains);
        System.out.println(coll.contains(new String("Tom")));
//       System.out.println(coll.contains(p));
        System.out.println(coll.contains(new Person("jerry", 20)));
        //2.containsAll(Collection call1)：判断形参coll1中的所有元素是否都存在于当前集合中
        Collection coll1 = Arrays.asList(123, 456);
        System.out.println(coll.containsAll(coll1));
    }
    @Test
    public void test2() {
        //3.remove(Object obj):从当前集合中移除obj元素
        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new Person("jerry", 20));
        coll.add(new String("Tom"));
        coll.add(false);
        coll.remove(123);
        System.out.println(coll);
        coll.remove(new Person("jerry", 20));
        System.out.println(coll);
        //4.removeAll(Collection coll1):从当前集合中移除coll1中所有的元素
        Collection coll1 = Arrays.asList(123, 456);
        coll.removeAll(coll1);
        System.out.println("............" + coll);
    }
    @Test
    public void test3() {
        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new Person("jerry", 20));
        coll.add(new String("Tom"));
        coll.add(false);
        //5.retainAll(Collection coll1):获取当前集合和coll1集合的交集，并返回给当前集合
//        Collection coll1 = Arrays.asList(123,456,789);
//        coll.retainAll(coll1);
//        System.out.println(coll);
        //6.equals(Object obj):要想返回true，需要当前集合和形参集合的元素都相同
        Collection coll1 = new ArrayList();
        coll1.add(123);
        coll1.add(456);
        coll1.add(new Person("jerry", 20));
        coll1.add(new String("Tom"));
        coll1.add(false);
        System.out.println(coll.equals(coll1));
    }
    @Test
    public void test4() {
        Collection coll = new ArrayList();
        coll.add(123);
        coll.add(456);
        coll.add(new Person("jerry", 20));
        coll.add(new String("Tom"));
        coll.add(false);
        //7.hashCode()：返回当前对象的哈希值
        System.out.println(coll.hashCode());
        //8.集合---->数组:toArray()
        Object[] arr = coll.toArray();
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
        //9.iterator():返回Iterator接口的实例，用于遍历集合元素，放在IteratorTest.java中
    }
}