Java HashMap键值存储和检索

Java Hashmap键值示例：

public void processHashMap() {    //add keys->value pairs to a hashmap:    HashMap hm = new HashMap();    hm.put(1, "godric gryfindor");    hm.put(2, "helga hufflepuff");    hm.put(3, "rowena ravenclaw");    hm.put(4, "salazaar slytherin");    //Then get data back out of it:    linkedList ll = new linkedList();    Iterator itr = hm.keySet().iterator();    while(itr.hasNext()) {        String key = itr.next();        ll.add(key);    }    System.out.print(ll);  //The key list will be printed.}