ArrayList<Integer> list = new ArrayList<>();//类型推断
list.add(78);
list.add(88);
list.add(77);
list.add(66);
//遍历方式一：
//for(Integer i : list){
//不需要强转
//System.out.println(i);
//}
//遍历方式二：
Iterator<Integer> iterator = list.iterator();
while(iterator.hasNext()){
System.out.println(iterator.next());

Map<String,Integer> map = new HashMap<String,Integer>();
map.put("Tom1",34);
map.put("Tom2",44);
map.put("Tom3",33);
map.put("Tom4",32);
//添加失败
//map.put(33, "Tom");
Set<Entry<String,Integer>> entrySet = map.entrySet();
Iterator<Entry<String,Integer>> iterator = entrySet.iterator();
while(iterator.hasNext()){
Entry<String,Integer> entry = iterator.next();
System.out.println(entry.getKey() + "--->" + entry.getValue());
}

List<String> strList = new ArrayList<String>();
Iterator<Customer> iterator = customers.iterator();

class GenericTest {
public static void main(String[] args) {
// 1、使用时：类似于Object，不等同于Object
ArrayList list = new ArrayList();
// list.add(new Date());//有风险
list.add("hello");
test(list);// 泛型擦除，编译不会类型检查
// ArrayList<Object> list2 = new ArrayList<Object>();
// test(list2);//一旦指定Object，编译会类型检查，必须按照Object处理
}
public static void test(ArrayList<String> list) {
String str = "";
for (String s : list) {
str += s + ",";
}
System.out.println("元素:" + str);
}
}