Java IO.pdf - Nguyen Dang Binh

Java I/O
from inside the class with established values, these checks are not absolutely necessary; but
they did help me catch several data entry errors as this class was developed.
A private constructor is unusual but not unheard of, especially when there are only a finite
number of valid objects. There are only a few dozen character blocks defined in Unicode 2.0,
each with a precise range. Declaring the constructor private prevents arbitrary blocks from
being created. Instead, a Java static block initializes all possible character blocks the first time
the class is loaded and stores them in a Hashtable called blocks. From this point forward,
the static getBlock() method can retrieve a particular block by its name. The names of the
blocks are used as keys in the hash table. The static getNames() method returns a list of the
available blocks, and the static getNumBlocks() method returns the number of blocks stored
in the hash table. There are several instance methods as well. The getStart(), getEnd(),
and getName() methods are accessors that return the values of the respective fields. Finally,
getCharactersInBlock() returns an array of chars containing each of the defined
characters in the block in sequence. However, many of the blocks contain undefined empty
spaces. For example, characters 983, 984, and 985 in the middle of the Greek block are not
defined. Testing each character in the range with the static method Character.isDefined()
weeds out undefined characters.
Example 14.1. The CharacterBlock Class
import java.util.*;
public class CharacterBlock {
String name;
int start;
int end;
private static Hashtable blocks = new Hashtable(66);
/* The blocks given here are as listed in The Unicode Standard,
Version 2.0. Ranges are given in hexadecimal as in that
document. It is not difficult to add additional blocks to this
list as they're defined.
*/
static {
// General Scripts
makeBlock("Basic Latin", 0x0000, 0x007F);
makeBlock("Latin-1 Supplement", 0x0080, 0x00FF);
makeBlock("Latin Extended-A", 0x0100, 0x017F);
makeBlock("Latin Extended-B", 0x0180, 0x024F);
makeBlock("IPA Extensions", 0x0250, 0x02AF);
makeBlock("Spacing Modifier Letters", 0x02B0, 0x02FF);
makeBlock("Combining Diacritical Marks", 0x0300, 0x036F);
makeBlock("Greek", 0x0370, 0x03FF);
makeBlock("Cyrillic", 0x0400, 0x04FF);
makeBlock("Armenian", 0x0530, 0x058F);
makeBlock("Hebrew", 0x0590, 0x05FF);
makeBlock("Arabic", 0x0600, 0x06FF);
makeBlock("Devanagari", 0x0900, 0x097F);
makeBlock("Bengali", 0x0980, 0x09FF);
makeBlock("Gurmukhi", 0x0A00, 0x0A7F);
makeBlock("Gujarati", 0x0A80, 0x0AFF);
makeBlock("Oriya", 0x0B00, 0x0B7F);
makeBlock("Tamil", 0x0B80, 0x0BFF);
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