103 lines
2.5 KiB
Java
103 lines
2.5 KiB
Java
//: patterns/recyclea/RecycleA.java
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// Recycling with RTTI.
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package patterns.recyclea;
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import java.util.*;
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import java.io.*;
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abstract class Trash {
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private double weight;
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Trash(double wt) { weight = wt; }
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abstract double value();
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double weight() { return weight; }
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// Sums the value of Trash in a bin:
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static void sumValue(List<Trash> bin) {
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Iterator<Trash> e = bin.iterator();
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double val = 0.0f;
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while(e.hasNext()) {
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// One kind of RTTI:
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// A dynamically-checked cast
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Trash t = e.next();
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// Polymorphism in action:
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val += t.weight() * t.value();
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System.out.println(
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"weight of " +
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// Using RTTI to get type
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// information about the class:
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t.getClass().getName() +
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" = " + t.weight());
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}
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System.out.println("Total value = " + val);
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}
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}
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class Aluminum extends Trash {
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static double val = 1.67f;
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Aluminum(double wt) { super(wt); }
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@Override
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double value() { return val; }
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static void value(double newval) {
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val = newval;
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}
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}
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class Paper extends Trash {
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static double val = 0.10f;
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Paper(double wt) { super(wt); }
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@Override
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double value() { return val; }
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static void value(double newval) {
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val = newval;
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}
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}
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class Glass extends Trash {
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static double val = 0.23f;
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Glass(double wt) { super(wt); }
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@Override
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double value() { return val; }
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static void value(double newval) {
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val = newval;
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}
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}
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public class RecycleA {
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public static void main(String[] args) {
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List<Trash> bin = new ArrayList<>();
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// Fill up the Trash bin:
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for(int i = 0; i < 30; i++)
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switch((int)(Math.random() * 3)) {
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case 0 :
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bin.add(new
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Aluminum(Math.random() * 100));
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break;
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case 1 :
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bin.add(new
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Paper(Math.random() * 100));
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break;
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case 2 :
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bin.add(new
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Glass(Math.random() * 100));
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}
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List<Trash>
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glassBin = new ArrayList<>(),
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paperBin = new ArrayList<>(),
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alBin = new ArrayList<>();
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Iterator<Trash> sorter = bin.iterator();
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// Sort the Trash:
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while(sorter.hasNext()) {
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Trash t = sorter.next();
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// RTTI to show class membership:
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if(t instanceof Aluminum)
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alBin.add(t);
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if(t instanceof Paper)
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paperBin.add(t);
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if(t instanceof Glass)
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glassBin.add(t);
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}
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Trash.sumValue(alBin);
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Trash.sumValue(paperBin);
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Trash.sumValue(glassBin);
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Trash.sumValue(bin);
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}
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} ///:~
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