Collection and Map and collections

The difference between the two:

Both are interfaces;

Collectoin is a top-level interface of the Java Collection framework, and the stored elements can be any type of object;

Map is a map interface of the Java collection framework that stores objects in the form of key-value pairs;

That is, the element stored in collection is an object, and map is the stored element that is a pair of pair of key-value pairs.

Collection<stirng> c=new arraylist<string> ();

Map<integer,string> map=new haspmap<integer,string> ();

C.add ("Hello");

C.add ("World");

Map.put (1, "Beijing");

Map.put (2, "tianjing");

Collection and Collections (class, All methods are static, the parameters of the method are all collections, so it is used to manipulate the array)

Collection<stirng> c=new arraylist<string> ();

Arraylist<string> list=new arraylist<stirng> ();

List.add ("Hello");

List.add ("etc");

Collections.sort (list);//Because collections is a class, and all methods are static, you can call a static method directly using the class name

for (stirng s:list) {

System.out.println (s);

}

Results: etc

Hello

Answer:

Collection cannot create objects directly, you can use their implementation classes to create a pair of images;

Collections is a Java collection framework of a class, is a tool class, defines a lot of static methods, you can manipulate the collection object;

Collection and Map and collections