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多项选择题Given a class whose instances， when found in a collection of objects， are sorted by using the compareTo（） method， which two statements are true？（）

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.

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1.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？（）

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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2.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；

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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.

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4.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（）；

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5.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

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6.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.

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7.单项选择题 What is the result？（）

A.Compilation fails.
B.An exception is thrown at runtime.
C.[608， 610， 612， 629] [608， 610]
D.[608， 610， 612， 629] [608， 610， 629]
E.[606， 608， 610， 612， 629] [608， 610]
F.[606， 608， 610， 612， 629] [608， 610， 629]

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8.单项选择题 Which statement is true？（）

A.The time to find the value from HashMap with a Person key depends on the size of the map.
B.Deleting a Person key from a HashMap will delete all map entries for all keys of type Person.
C.Inserting a second Person object into a HashSet will cause the first Person object to be removed as a duplicate.
D.The time to determine whether a Person object is contained in a HashSet is constant and does NOT depend on the size of the map.

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9.单项选择题 What is the result？（）

A.[1， 2， 3， 5]
B.[2， 1， 3， 5]
C.[2， 5， 3， 1]
D.[5， 3， 2， 1]
E.[1， 3， 5， 2]
F.Compilation fails.
G.An exception is thrown at runtime.

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10.单项选择题 Which statement is true？（）

A.Compilation fails because the hashCode method is not overridden.
B.A HashSet could contain multiple Person objects with the same name.
C.All Person objects will have the same hash code because the hashCode method is not overridden.
D.If a HashSet contains more than one Person object with name="Fred"， then removing another Person， also with name="Fred"， will remove them all.

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