集合

import java.util.LinkedHashSet;
import java.util.Set;


public class set
{
    public static void main(String[] args)
    {
        String[]s= {"a","b","c","d","e","d","a","d"};
        Set <String>set=new LinkedHashSet<String>();
        for(String i: s)
        if(!set.add(i))
        {
            System.out.println("重复元素是:"+i);
        }
    }

}
由于linkhashset.hashset.hashtree都实现了set的接口
所以上面的linkedhashset可以替换成hashset或者hashtree