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
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