多项选择题
A.The class implements java.lang.Comparable.
B.The class implements java.util.Comparator.
C.The interface used to implement sorting allows this class to define only one sort sequence.
D.The interface used to implement sorting allows this class to define many different sort sequences.
多项选择题 A programmer is developing a class Key， that will be used as a key in a standard java.util.HashMap. Which two methods should be overridden to assure that Key works correctly as a key？（）
单项选择题 What is the appropriate definition of the hashCode method in class Person？（）
单项选择题 Which statement is true about the set variable on line 12？（）