JAVA Foundation (17)-Set Collection, HashSet

Set collection

Duplicate elements are not allowed. Same method as Collection. There is only one way to retrieve the Set collection: iterator.

Common implementation classes:

HashSet：

 

HashSet

package demo;
import java.util.*;
public class Demo {
	public static void main(String[] args) {	
		
		Set set=new HashSet();
		
		set.add("haha");
		set.add("aawdwad");
		set.add("haha");//这里故意重复元素
		set.add("啊啊啊111");
		set.add("灌灌灌灌11222");
		//取出元素--只能用迭代器
		for(Iterator it=set.iterator();it.hasNext();) {
			System.out.println(it.next());//打印结果不包含重复元素
			
		}
		
	}
			
}