87 lines
2.5 KiB
Java
87 lines
2.5 KiB
Java
|
//: patterns/trash/Trash.java
|
||
|
|
// Base class for Trash recycling examples.
|
||
|
|
package patterns.trash;
|
||
|
|
import java.util.*;
|
||
|
|
import java.lang.reflect.*;
|
||
|
|
|
||
|
|
public abstract class Trash {
|
||
|
|
private double weight;
|
||
|
|
Trash(double wt) { weight = wt; }
|
||
|
|
Trash() {}
|
||
|
|
public abstract double value();
|
||
|
|
public double weight() { return weight; }
|
||
|
|
// Sums the value of Trash in a bin:
|
||
|
|
public static void sumValue(ArrayList bin) {
|
||
|
|
Iterator e = bin.iterator();
|
||
|
|
double val = 0.0f;
|
||
|
|
while(e.hasNext()) {
|
||
|
|
// One kind of RTTI:
|
||
|
|
// A dynamically-checked cast
|
||
|
|
Trash t = (Trash)e.next();
|
||
|
|
val += t.weight() * t.value();
|
||
|
|
System.out.println(
|
||
|
|
"weight of " +
|
||
|
|
// Using RTTI to get type
|
||
|
|
// information about the class:
|
||
|
|
t.getClass().getName() +
|
||
|
|
" = " + t.weight());
|
||
|
|
}
|
||
|
|
System.out.println("Total value = " + val);
|
||
|
|
}
|
||
|
|
// Remainder of class provides support for
|
||
|
|
// prototyping:
|
||
|
|
public static class PrototypeNotFoundException
|
||
|
|
extends Exception {}
|
||
|
|
public static class CannotCreateTrashException
|
||
|
|
extends Exception {}
|
||
|
|
private static ArrayList trashTypes =
|
||
|
|
new ArrayList();
|
||
|
|
public static Trash factory(Info info)
|
||
|
|
throws PrototypeNotFoundException,
|
||
|
|
CannotCreateTrashException {
|
||
|
|
for(int i = 0; i < trashTypes.size(); i++) {
|
||
|
|
// Somehow determine the new type
|
||
|
|
// to create, and create one:
|
||
|
|
Class tc =
|
||
|
|
(Class)trashTypes.get(i);
|
||
|
|
if (tc.getName().indexOf(info.id) != -1) {
|
||
|
|
try {
|
||
|
|
// Get the dynamic constructor method
|
||
|
|
// that takes a double argument:
|
||
|
|
Constructor ctor =
|
||
|
|
tc.getConstructor(
|
||
|
|
new Class[] {double.class});
|
||
|
|
// Call the constructor to create a
|
||
|
|
// new object:
|
||
|
|
return (Trash)ctor.newInstance(
|
||
|
|
new Object[]{new Double(info.data)});
|
||
|
|
} catch(Exception ex) {
|
||
|
|
ex.printStackTrace();
|
||
|
|
throw new CannotCreateTrashException();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
// Class was not in the list. Try to load it,
|
||
|
|
// but it must be in your class path!
|
||
|
|
try {
|
||
|
|
System.out.println("Loading " + info.id);
|
||
|
|
trashTypes.add(
|
||
|
|
Class.forName(info.id));
|
||
|
|
} catch(Exception e) {
|
||
|
|
e.printStackTrace();
|
||
|
|
throw new PrototypeNotFoundException();
|
||
|
|
}
|
||
|
|
// Loaded successfully. Recursive call
|
||
|
|
// should work this time:
|
||
|
|
return factory(info);
|
||
|
|
}
|
||
|
|
public static class Info {
|
||
|
|
public String id;
|
||
|
|
public double data;
|
||
|
|
public Info(String name, double data) {
|
||
|
|
id = name;
|
||
|
|
this.data = data;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
} ///:~
|