Java Reference
In-Depth Information
return
aList.get(0);
}
3.
public
static
boolean
noNull(Set<?> s)
{
return
(s.remove(
null
));
}
4.
No.
5.
It would make more sense to make it a derived class of the
ArrayList<T>
class.
Then the elements are ordered. You can ensure against repeated elements by
redefining all methods that add elements so that the methods check to see if the
element is already in the class before entering it. A derived class of the
Hash-
Set<T>
class would automatically ensure that no element is repeated, but it
would seem to take a good deal of work to maintain the elements in order.
6.
Multiple copies of some element are not allowed as a key, but are allowed as values.
7.
The variable would be defined as:
HashMap<Integer,Employee> employeeMap =
new
HashMap<Integer,Employee>(100);
If the ID numbers are between 0 and 100 then the map will work, but a simple
array or
ArrayList
might be a more appropriate data structure.
8.
A
HashSet<T>
does not. An
ArrayList<T>
does.
9.
The answer to both questions is the same: They will return the same element.
Programming Projects
Many of these Programming Projects can be solved using AW's CodeMate.
To access these please go to:
www.aw-bc.com/codemate
.
1.
Redo Programming Project 8 in Chapter 6, but this time do it for a vector of strings
to be sorted into lexicographic order.
2.
The Sieve of Erastothenes is an ancient algorithm that generates prime numbers.
Consider the list of numbers from 2 to 10 below:
2 3 4 5 6 7 8 9 10
The algorithm starts with the first prime number in the list, which is 2, and then
iterates through the remainder of the list, removing any number that is a
multiple of 2 (in this case, 4, 6, 8, and 10), leaving:
2 3 5 7 9
We then repeat the process with the second prime number in the list, which is 3,
and then iterate through the remainder of the list removing any number that is a
multiple of 3 (in this case 9), leaving:
2
3
5
7
