多项选择题

A.public int hashCode（）B.public void hashCode（）C.public……

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？（）

A.public int hashCode（）
B.public void hashCode（）
C.public int compareTo（Object o）
D.public boolean equals（Object o）
E.public boolean compareTo（Key k）

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热门试题

单项选择题What is the appropriate definition of the hashCode method in class Person？（）

A.return super.hashCode（）；
B.return name.hashCode（） + age * 7；
C.return name.hashCode（） + comment.hashCode（） / 2；
D.return name.hashCode（） + comment.hashCode（） / 2- age * 3；

单项选择题Which statement is true about the set variable on line 12？（）

A.The set variable contains all six elements from the coll collection， and the order is guaranteed to be preserved.
B.The set variable contains only three elements from the coll collection， and the order is guaranteed to be preserved.
C.The set variable contains all six elements from the coll collection， but the order is NOT guaranteed to be preserved.
D.The set variable contains only three elements from the coll collection， but the order is NOT guaranteed to be preserved.

单项选择题Which code， inserted at line 4， guarantees that this program will output [1， 2]？（）

A.Set set = new TreeSet（）；
B.Set set = new HashSet（）；
C.Set set = new SortedSet（）；
D.List set = new SortedList（）；
E.Set set = new LinkedHashSet（）；

单项选择题A programmer must create a generic class MinMax and the type parameter of MinMax must implement Comparable. Which implementation of MinMax will compile？（）

A.A
B.B
C.C
D.D

单项选择题A programmer iterates over the TreeSet and prints the name of each Drink object. What is the result？（）

A.Tea
B.Coffee
C.Coffee Tea
D.Compilation fails.
E.The code runs with no output.
F.An exception is thrown at runtime.