Java Reference
In-Depth Information
for(int i = 0 ; i < filmCast.size() ; ++i) {
System.out.println(filmCast.get(i));
}
The collection-based
for
loop is the simplest way of all for listing the contents of the vector:
for(Person person : filmCast) {
System.out.println(person);
}
To output the space remaining in the vector, you calculate the difference between the capacity and the
size:
System.out.println("\nThe vector currently has room for "
+ (filmCast.capacity() - count) + " more people.");
This is interesting but irrelevant because the vector accommodates as many stars as you care to enter.
The static
readPerson()
method is a convenient way of managing the input. The input source is the
static class member defined by the following statement:
static BufferedReader keyboard = new BufferedReader(
new
InputStreamReader(System.in));
The keyboard object is
System.in
wrapped in an
InputStreamReader
object that is wrapped in a
BufferedReader
object. The
InputStreamReader
object provides conversion of the input from the
byte stream
System.in
to characters. The
BufferedReader
object buffers the data read from the
In-
putStreamReader
. Because the input consists of a series of strings entered one to a line, the
readLine()
method does everything you need. The calls to
readLine()
is in a
try
block because it can throw an
IOException
. The call to the
trim()
method for the
String
object returned by the
readLine()
method
removes leading or trailing blanks.
Sorting a Collection
The output from the last example appears in the sequence in which you enter it. If you want to arrange them
in alphabetical order you could write your own method to sort
Person
objects in the
filmCast
object, but it
is a lot less trouble to take advantage of another feature of the
java.util
package, the
Collections
class
— not to be confused with the
Collection<>
interface. The
Collections
class defines a variety of handy
static utility methods that you can apply to collections, and one of them happens to be a
sort()
method.
The
sort()
method only sorts lists — that is, collections that implement the
List<>
interface. Obviously
there has to be some way for the
sort()
method to determine the order of objects from the list that it is
sorting — in your case,
Person
objects. The most suitable way to do this is to implement the
Comparable<>
interface in the
Person
class. As you know, the
Comparable<>
interface declares only one method,
com-
pareTo()
. You saw this method in the previous chapter so you know it returns -1, 0, or +1 depending on
whether the current object is less than, equal to, or greater than the argument. If the
Comparable<>
interface
is implemented for the type of object stored in a collection, you can just pass the collection object as an
argument to the
sort()
method. The collection is sorted in place so there is no return value.
