4.11 Java4060r: review  (Page 3/3)

• add(int index, Object element)
• get(int index)

Valid index values are positive integers that begin with zero.

Another version of the add method takes a reference to an object as an incoming parameter and appends the specified element to the end of thecollection.

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Answer 17

False. Unlike collections that implement the SortedSet interface, the order of the elements in a collection that implements the List interface is not based on the values of the objects referred to by the elements in thelist.

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Answer 16

True. For example, the add method of the Set interface stipulates the following:

"Adds the specified element to this set if it is not already present."

On the other hand, the add method of the Collection interface simply states:

"Ensures that this collection contains the specified element."

Thus, the contract for the add method of an object of a class that implements the Set interface is more specialized than the contract for the add method of an object of a class that implements the Collection interface.

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Answer 15

False. You can cause the sort order to ignore case by providing an object of a class that implements the Comparator interface, and which defines the compare method and the equals method in such a way as to eliminate case considerations for comparisons of String objects.

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Answer 14

True.

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Answer 13

False. Implementations of the interface named SortedSet do maintain their elements in sorted order. However, that order is not necessarilyascending. When an object is instantiated from a class that implements the SortedSet interface, the sorting order for that object can be established by providing an object instantiated from aclass that implements the Comparator interface. In that case, the author of the class that implements the Comparator interface determines the order imposed on the elements in the collection.

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Answer 12

False. Not all implementations of the Collection interface maintain the elements in ascending sort order. Some may, and others do not. For example,implementations of the List interface (such as ArrayList ) do not maintain their elements in sorted order at all. In other words, the position of an element in an ArrayList does not depend on the value of the element.

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Answer 11

True.

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Answer 10

False. An ordered collection is one in which each element in the collection has a specific position specified by an index.

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Answer 9

False. An ordered collection is not the same as a sorted collection.

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Answer 8

True, according to Oracle.

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Answer 7

True, according to Oracle.

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Answer 6

False.

The Java Collections Framework doesn't provide any direct implementations of the Collection interface. All of the implementations of the interfaces in the Collection hierarchy implement one of the sub-interfaces of the Collection interface. In the case of the ArrayList class, that sub-interface is the List interface, which extends the Collection interface.

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Answer 5

True.

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Answer 4

False. The TreeSet class is not a direct implementation of the Collection interface. Rather, the TreeSet class is a direct implementation of the SortedSet interface. The SortedSet interface extends the Set interface, and the Set interface extends the Collection interface.

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Answer 3

False. A Set object cannot contain duplicate elements, but a List object can contain duplicate elements.

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Answer 2

False. One of the trees, which consists of six interfaces, is rooted in the interface named Collection . The other tree, which consists of two interfaces, is rooted in the interface named Map .

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Answer 1

True.

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Miscellaneous

This section contains a variety of miscellaneous information.

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