Objects and classes - Data Structures and Problem Solving Using Java - page 86

figure 3.10
An example of a
static initializer

1 public class Squares
2 {
3 private static double [ ] squareRoots = new double[ 100 ];
4
5 static
6 {
7 for( int i = 0; i < squareRoots.length; i++ )
8 squareRoots[ i ] = Math.sqrt( ( double ) i );
9 }
10 // Rest of class
11 }

3.6.6 static initializers

Static fields are initialized when the class is loaded. Occasionally, we need a
complex initialization. For instance, suppose we need a static array that stores
the square roots of the first 100 integers. It would be best to have these values
computed automatically. One possibility is to provide a static method and
require the programmer to call it prior to using the array.

An alternative is the static initializer . An example is shown in Figure 3.10.
There, the static initializer extends from lines 5 to 9. The simplest use of the
static initializer places initialization code for the static fields in a block that
is preceded by the keyword static . The static initializer must follow the dec-
laration of the static member.

A static initializer is
a block of code that
is used to initialize
static fields.

example: implementing
a BigRational class

3.7

In this section, we write a class that illustrates many of the concepts that have
been described in this chapter, including

public static final constants n

n

use of an existing class, namely BigInteger

multiple constructors

n

n

throwing exceptions

implementing a set of accessors n

n

implementing equals and toString