数据结构1-8-1（哈希表）

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Random;

public class Hash {
    public static void main(String[] args) {
        testHashMap();
    }

    public static void testHashMap() {
        Random r = new Random();

        HashMap map = new HashMap();
        map.put("one",r.nextInt(10));
        map.put("two",r.nextInt(10));
        map.put("three",r.nextInt(10));

        System.out.println("map"+map);
        Iterator iterator = map.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry entry = (Map.Entry) iterator.next();
            System.out.println(entry);
        }
        System.out.println("size:"+map.size());
        System.out.println("contain key one:"+ map.containsKey("one"));
        System.out.println("contain value 4:"+ map.containsValue(2));

        map.remove("four");

        map.clear();
        System.out.println("map是否为空："+map.isEmpty());
    }
}