map的输出
Map<String,String> map=new HashMap<>();
map.put("a","a");
map.put("b","b");
map.put("c","c");
Set<Map.Entry<String, String>> entries = map.entrySet();
Iterator<Map.Entry<String, String>> iterator = entries.iterator();
while (iterator.hasNext()){
Map.Entry<String, String> entry = iterator.next();
System.out.println(entry);
}