范型，迭代Map

Map<Integer,String> map = new HashMap<Integer,String>();(LinkedHashMap为有序的map)
map.put(1,"a");
map.put(2,"b");
Set<Map.Entry<Integer,String>> set = map.entrySet();
Iteratord迭代：
Iterator<Map.Entry<Integer,String>> it = set.iterator();
while(it.hashNext()){
Map.Entry<Integer,String> entry = it.next();
int key = entry.getKey();
String value = entry.getValue();
}
增强for循环迭代：
for(<Map.Entry<Integer,String>> entry : map.entrySet()){
int key = entry.getKey();
String value = entry.getValue();
}