Map<String,String> map = new HashMap<String,String>();

map.put("name","zhangsan");

map.put("sno","0812");

map.put("cno","3-105");

//将map集合的所有键set到集合中，keySet()

Set<String> set = map.keySet();

Iterator<String> it = set.iterator();

while(it.hasNext()){

     String key = it.next();

     String value = map.get(key);

     System.out.println("key==="+key+",value==="+value);

}

Set<Map.Entry<String,String>> es = map.entrySet();

Iterator<String> it = es.iterator();

while(it.hasNext()){

   Map.Entry<String,String> mey = it.next();

   String key = mey.getKey();

   String value = mey.getValue();

   System.out.println("key==="+key+",value==="+value);

}