Java Reference
In-Depth Information
A Collection of Useful Classes
In this chapter we'll be looking at some more very useful classes in the
java.util
package but this
time they are not collection classes - just a collection of classes. We will also be looking at the facilities
provided by classes in the
java.util.regex
package that implements regular expressions in Java.
Support for regular expressions is a very powerful and important addition to Java.
In this chapter you will learn:
How to use the static methods in the
Arrays
class for filling, comparing, sorting, and
searching arrays
❑
How to use the
Observable
class and the
Observer
interface to communicate between objects
❑
What facilities the
Random
class provides
❑
How to create and use
Date
and
Calendar
objects
❑
What regular expressions are and how you can create and use them
❑
Utility Methods for Arrays
The
Arrays
class in
java.util
provides you with a set of static methods for operating on arrays.
There are methods for sorting and searching arrays, as well as methods for comparing two arrays of
elements of a basic type. You also have methods for filling arrays of elements with a given value. Let's
look at the simplest method first, the
fill()
method for filling an array.
Filling an Array
The need to fill an array with a specific value arises quite often. The
fill()
method comes in a
number of overloaded versions of the form:
fill(type [] array, type value)
Here
type
is a placeholder for the types supported by various versions of the method. The method