removeAll方法原来是这样的

ayis

 
 

boolean

removeAll(Collection<?> c)           Removes all of this collection's elements that are also contained in the specified collection (optional operation).

 
 
 
to mysurprise ,the removeAll method has a arguement，its function is to remove all of its elements that are also contained in the specified collection. this method is defined in the interface Collection. Both  Interface Set and Interface  List are subinterfaces of Collection.