* This field is initialized by a static initializer so that * we can catch any exceptions thrown by URI(String) and * transform them into a RuntimeException, since this should * never happen but should be reported properly if it ever does. */ private static URI identifierURI; /** * RuntimeException that wraps an Exception thrown during the * creation of identifierURI, null if none. */ private static RuntimeException earlyException; /** * Single instance of BooleanAttribute that represents true. * Initialized by the static initializer below. */ private static BooleanAttribute trueInstance; /** * Single instance of BooleanAttribute that represents false. * Initialized by the static initializer below. */ private static BooleanAttribute falseInstance; /** * Static initializer that initializes many static fields. *
* It is possible identifierURI
* class field so that we can catch any exceptions thrown
* by URI(String) and transform them into a RuntimeException.
* Such exceptions should never happen but should be reported
* properly if they ever do.
*/
static {
try {
identifierURI = new URI(identifier);
trueInstance = new BooleanAttribute(true);
falseInstance = new BooleanAttribute(false);
} catch (Exception e) {
earlyException = new IllegalArgumentException();
earlyException.initCause(e);
}
};
/**
* The actual boolean value that this object represents.
*/
private boolean value;
/**
* Creates a new BooleanAttribute that represents
* the boolean value supplied.
*
* This constructor is private because it should not be used by
* anyone other than the static initializer in this class.
* Instead, please use one of the getInstance methods, which
* will ensure that only two BooleanAttribute objects are created,
* thus avoiding excess object creation.
*/
private BooleanAttribute(boolean value) {
super(identifierURI);
this.value = value;
}
/**
* Returns a BooleanAttribute that represents
* the xs:boolean at a particular DOM node.
*
* @param root the Node that contains the desired value
* @return a BooleanAttribute representing the
* appropriate value (null if there is a parsing error)
*/
public static BooleanAttribute getInstance(Node root)
throws ParsingException
{
return getInstance(root.getFirstChild().getNodeValue());
}
/**
* Returns a BooleanAttribute that represents
* the xs:boolean value indicated by the string provided.
*
* @param value a string representing the desired value
* @return a BooleanAttribute representing the
* appropriate value (null if there is a parsing error)
*/
public static BooleanAttribute getInstance(String value)
throws ParsingException
{
// Shouldn't happen, but just in case...
if (earlyException != null)
throw earlyException;
if (value.equals("true"))
return trueInstance;
if (value.equals("false"))
return falseInstance;
throw new ParsingException("Boolean string must be true or false");
}
/**
* Returns a BooleanAttribute that represents
* the boolean value provided.
*
* @param value a boolean representing the desired value
* @return a BooleanAttribute representing the
* appropriate value
*/
public static BooleanAttribute getInstance(boolean value) {
// Shouldn't happen, but just in case...
if (earlyException != null)
throw earlyException;
if (value)
return trueInstance;
else
return falseInstance;
}
/**
* Returns a BooleanAttribute that represents
* a true value.
*
* @return a BooleanAttribute representing a
* true value
*/
public static BooleanAttribute getTrueInstance() {
// Shouldn't happen, but just in case...
if (earlyException != null)
throw earlyException;
return trueInstance;
}
/**
* Returns a BooleanAttribute that represents
* a false value.
*
* @return a BooleanAttribute representing a
* false value
*/
public static BooleanAttribute getFalseInstance() {
// Shouldn't happen, but just in case...
if (earlyException != null)
throw earlyException;
return falseInstance;
}
/**
* Returns the boolean value represented by this object.
*
* @return the boolean value
*/
public boolean getValue() {
return value;
}
/**
* Returns true if the input is an instance of this class and if its
* value equals the value contained in this class.
*
* @param o the object to compare
*
* @return true if this object and the input represent the same value
*/
public boolean equals(Object o) {
if (! (o instanceof BooleanAttribute))
return false;
BooleanAttribute other = (BooleanAttribute)o;
return (value == other.value);
}
/**
* Returns the hashcode value used to index and compare this object with
* others of the same type. Typically this is the hashcode of the backing
* data object.
*
* @return the object's hashcode value
*/
public int hashCode() {
// these numbers come from the javadoc for java.lang.Boolean...no,
// really, they do. I can't imagine what they were thinking...
return (value ? 1231 : 1237);
}
/**
*
*/
public String encode() {
return (value ? "true" : "false");
}
}