[Java in NetBeans] Lesson 14. ArrayList and Collections

这个课程的参考视频和图片来自youtube。

    主要学到的知识点有：

1. Collection: container that contians objects.

2. Difference between Collection and Array 

collection	array	example
Dynamic siized	fixed sized	int[] grades = new int[20]
cannot	Primitive types	ArrayList<integer> grades = new ArrayList<>();

 

 

 

 

 

note: int =>  Integer

         double => Double

 

3. ArrayList: an implemnetation of a collection. 

• Create a ArrayList. (assume that we have a Card class has number and suit)

ArrayList<Card> cards = new ArrayList<>():

• Add element in the ArrayList

cards.add(new Card(8, Diamond));

cards.add(new Card(6, Diamond));

• Remove element in the ArrayList

Card temp = cards.remove(0); // will move the first elemnt in the ArrayList

• Set element in the ArrayList

cards.set(0, new Card(3, Diamond)); // will set the first elemnt in the ArrayList

•  Get element in the ArrayList

cards.get(0); // will get the first elemnt in the ArrayList

•  Insert element in the ArrayList

cards.add(0, new Card(1, Diamond)); // will add Diamond 1 at the first elemnt in the ArrayList