JDBC连接数据库

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 在当前项目下新建一个Floder文件

然后将下载的驱动导入此文件，前四种方法仅供了解，重点第五种方法，需要创建一个配置文件

 @Test
    public void test1() {
        ArrayList coll = new ArrayList();
        coll.add(new Person("jerry",20));
        coll.add(123);
        coll.add(456);
        coll.add(new String ("tom"));
        coll.add(false);

        //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")));
        System.out.println(coll.contains(new Person("jerry", 20)));
//2.ContainsSAll(Collection coll1):判断形参对应的coll1是否都存在于当前集合中
        Collection coll1 = Arrays.asList(123,4567);
        System.out.println(coll.containsAll(coll1));
//        coll.forEach(System.out::println);
    }

    @Test
    public void test2(){
//        3.remove(Object obj)
        Collection coll = new ArrayList();
        coll.add(new Person("jerry",20));
        coll.add(123);
        coll.add(456);
        coll.add(new String ("tom"));
        coll.add(false);
        boolean remove = coll.remove(1234);
        coll.remove(new Person("jerry",20));
        System.out.println(coll);
        System.out.println("************");
//        System.out.println(remove);
        //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(new Person("jerry",20));
        coll.add(123);
        coll.add(456);
        coll.add(new String ("tom"));
        coll.add(false);
        //5. retainAll(Collection coll1)交集：获取当前集合和coll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，需要判断当前集合和形参集合得元素是否相同
        Collection coll1 = new ArrayList();
        coll1.add(new Person("jerry",20));
        coll1.add(456);
        coll1.add(123);
        coll1.add(new String ("tom"));
        coll1.add(false);
        System.out.println(coll.equals(coll1));
    }
    @Test
    public void test4(){
        Collection coll = new ArrayList();
        coll.add(new Person("jerry",20));
        coll.add(123);
        coll.add(456);
        coll.add(new String ("tom"));
        coll.add(false);
        //7. hasCode()：返回当前对象的哈希值
        System.out.println(coll.hashCode());
        //8.集合----》数组
        Object[] arr = coll.toArray();
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
        //拓展：数组转换为集合:调用Arrays类得静态方法aslist()
        List<String> list = Arrays.asList(new String[]{"AA", "BB", "CC"});
        System.out.println(list);
//        List<int[]> arr1 = Arrays.asList(new int[]{123, 456});
        List arr1 = Arrays.asList(123.456);
        System.out.println(arr1.size());
        List arr2 = Arrays.asList(new Integer[]{123,456});
        System.out.println(arr2.size());
    //9.iterator():返回iterator接口的实例，用于遍历集合元素，放在IteratorTest.java中


    }