java map

判断key是否存在

boolean flag=map.containsKey("opt")  

　map遍历

Map<Integer, Integer> map = new HashMap<Integer, Integer>(); 
for (Map.Entry<Integer, Integer> entry : map.entrySet()) { 
  System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); 
}

　　或者

Map<Integer, Integer> map = new HashMap<Integer, Integer>(); 
Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator(); 
while (entries.hasNext()) { 
  Map.Entry<Integer, Integer> entry = entries.next(); 
  System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); 
}