JAVA的集合遍历

通用遍历

不适用于Map，因为它不继承于Collection接口

for循环

    for (int i = 0; i < list.size(); i++) {
         int j = (Integer) list.get(i);
     }

增强for

     for(int i : list) {
         System.out.println(i);
     }

迭代器遍历

	Iterator it = list.iterator();
	while (it.hasNext()) {
		Object item = it.next();
	}

forEach

    list.forEach(item->{
        System.out.println(item);
    });

Map的遍历

Map对象

Map<String, String> mapList = new HashMap<>();

通过key遍历

   for(String k : mapList.keySet()) {
       String val = mapList.get(k);
   }

迭代器遍历

	Iterator<Map.Entry<String,String>> it = mapList.entrySet().iterator();
	while (it.hasNext()) {
		Map.Entry<String,String> item = it.next();
	}

通过value遍历

   for(String v : mapList.values()) {
   }

通过Map.entrySet遍历

    for(Map.Entry<String, String> entry:mapList.entrySet()) {
        String k = entry.getKey();
        String v = entry.getValue();
    }

forEach遍历

   mapList.forEach((k,v)->{
    });