2016/5/29 Study Record

1. Examples of polymorphic and dynamic bindings help to understand

1  Public classTest {2      Public Static voidMain (string[] args) {3         NewA ();4         NewB ();5     }6 }7 8 classA {9      Public inti = 7;Ten  One      PublicA () { ASetI (20); -System.out.println ("The number of I in A is" +i); -     } the  -      Public voidSetI (inti) { -          This. i = 2 *i; -     } +  - } +  A classBextendsA { at      PublicB () { -System.out.println ("The I in B is" +i); -     } -  -      Public voidSetI (inti) { -          This. i = 3 *i; in     } -}

Output to

The number of I in Ais 60

View Code

Usage of the 2.ArrayList class [Object list/object array]

The ArrayList class contains methods that have +arraylist ()/+add ()/+add (Index,inti)/+clear/+contains/+get (Intdex)/+indexof (object)/+isempty () /+remove ()/+set (Index,inti)

Creation mode arraylist<string> list = new arraylist<> ();

The ArrayList class can use traversal, which is the same as the array;

Create a list of objects from an array {

string[] array = new STRING[5];

arraylist<string> list = new Arraylist<> (arrays.aslist (array)); This is done using the Aslist method of the arrays class for replication.

}

In turn, create an array from the object list {

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

String[] B = new string[list.size ()];

List.toarray (b);

}

If the array contains numeric objects, it can be sorted as follows

Double [] array = {1.2,1,3,5.3,0.3};

Arrays.sort (array);

The same for object list　

arraylist<string> list = new Arraylist<> (arrays.aslist (array));

Java.util.Collections.sort (list);

There are many other uses of collections which are very convenient. For example Collections.max (list)/collections.min (list)/collections.shuffle (list)//scrambled

　　

　

2016/5/29 Study Record