测试LinkedHashSet中的基本方法与规则

import java.util.*;
class test  
{
    public static void main (String[] args) throws java.lang.Exception
    {

        Set<String> set1=new LinkedHashSet<>();
        set1.add("london");
        set1.add("paris");
        set1.add("beijing");
        set1.add("sun");
        set1.add("new york");
        set1.add("new york");
        System.out.println("set1 is "+set1);
        System.out.println(set1.size()+" elements in set1");
        for(String s:set1)
        System.out.println(s.toUpperCase());
    }
}