import java.util.HashSet;
import java.util.Iterator;
import java.util.Random;

public class Set {

    public static void main(String[] args) {
        // HashSet
        HashSet<String> hs = new HashSet<String>();
        hs.add("a");
        hs.add("b");
        hs.add("n");
        hs.add("1");
        System.out.println(hs);
        // 遍历
        Iterator it = hs.iterator();
        while (it.hasNext()) {
            System.out.println(it.next());

        }
        System.out.println("--------------");
        //foreach
        for (String str : hs) {
            System.out.println(str);
        }
        System.out.println("------------------");
        Random R =new Random();
        HashSet<Integer> hs1 = new HashSet<Integer>();
        while(hs1.size()<10){
            int res =  R.nextInt(20)+1;
            hs1.add(res);

        }
        System.out.println(hs1);
    }

}