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This article introduces you how to express the Collection collection, the content is very detailed, interested friends can refer to, I hope it can be helpful to you.

Traversal of a set

Class Demo_Collection {

Public static void main (String [] args) {

Collection c = new ArrayList (); / / Collection is an interface, so you cannot create an object directly, so create a subclass object

C.add ("a"); / / call the add () method to add elements to the collection

C.add ("a")

C.add ("a")

C.add ("a")

/ *

Object [] arr = c.toArray (); / / convert a collection to a number

For (int I = 0; I

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