Mega Code Archive
Demonstrates Dynamic class type checking
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/*
* file: DynamicTypeChecking.java
* package: oreilly.hcj.reflection
*
* This software is granted under the terms of the Common Public License,
* CPL, which may be found at the following URL:
* http://www-124.ibm.com/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags.
* All Rights are Reserved by the various authors.
*
########## DO NOT EDIT ABOVE THIS LINE ########## */
import java.io.Serializable;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
/**
* Demonstrates Dynamic class type checking.
*
* @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.3 $
*/
public class DynamicTypeChecking {
/**
* Demonstrates usage of <tt>isAssignableFrom</tt> on a class object.
*
* @param dataType
* The data type to check.
*
* @return The value <tt>true</tt> if the class is a descendant of
* <tt>java.lang.Number</tt> or <tt>false</tt> if it isnt.
*/
public static boolean isNumber(final Class dataType) {
return Number.class.isAssignableFrom(dataType);
}
/**
* Demonstration Method.
*
* @param args
* Command Line arguments.
*/
public static void main(final String[] args) {
final Set classes = new HashSet();
classes.add(Class.class);
classes.add(Comparable.class);
classes.add(Serializable.class);
classes.add(Integer.class);
classes.add(int.class);
classes.add(Float[].class);
classes.add(String.class);
classes.add(double[].class);
classes.add(boolean.class);
System.out.println("Using isAssignableFrom:");
useAssignable(classes);
System.out.println("\nUsing isInstance:");
useIsInstance(classes);
}
/**
* Demonstrates use of <tt>isAssignableFrom</tt> on objects in a set.
*
* @param inputSet
* The set to check.
*/
public static void useAssignable(final Set inputSet) {
final Iterator iter = inputSet.iterator();
Object obj = null;
while (iter.hasNext()) {
obj = iter.next();
if (obj != null) {
if (Number.class.isAssignableFrom(obj.getClass())) {
System.out.println(obj);
}
}
}
}
/**
* Demonstrates usage of <tt>isInstance</tt> on objects in a set.
*
* @param inputSet
* The set to check.
*/
public static void useIsInstance(final Set inputSet) {
final Iterator iter = inputSet.iterator();
Object obj = null;
while (iter.hasNext()) {
obj = iter.next();
if (Number.class.isInstance(obj)) {
System.out.println(obj);
}
}
}
/**
* Demonstration method for class comparison based on passed class and object.
*
* @param dataType
* The data type to check.
* @param inputSet
* The input set to check.
*
* @throws NullPointerException
* If the data type given is null.
*/
public static void useIsInstance2(final Class dataType, final Set inputSet) {
if (dataType == null) {
throw new NullPointerException();
}
final Iterator iter = inputSet.iterator();
Object obj = null;
while (iter.hasNext()) {
obj = iter.next();
if (dataType.isInstance(obj)) {
System.out.println(obj);
}
}
}
/**
* A bad version of useInstance. If you uncomment this method you will get a
* compiler error.
*/
// public static void useIsInstance3(final Class dataType, final Set inputSet)
// {
// final Iterator iter = inputSet.iterator();
// Object obj = null;
// while (iter.hasNext()) {
// obj = iter.next();
// if (obj instanceof dataType) {
// System.out.println(obj);
// }
}
/* ########## End of File ########## */
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