69 lines
1.6 KiB
Java
69 lines
1.6 KiB
Java
//: patterns/doubledispatch/DoubleDispatch.java
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// Using multiple dispatching to handle more
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// than one unknown type during a method call.
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package patterns.doubledispatch;
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import patterns.trash.*;
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import java.util.*;
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class AluminumBin extends TypedBin {
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@Override
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public boolean add(DDAluminum a) {
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return addIt(a);
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}
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}
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class PaperBin extends TypedBin {
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@Override
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public boolean add(DDPaper a) {
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return addIt(a);
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}
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}
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class GlassBin extends TypedBin {
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@Override
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public boolean add(DDGlass a) {
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return addIt(a);
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}
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}
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class CardboardBin extends TypedBin {
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@Override
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public boolean add(DDCardboard a) {
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return addIt(a);
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}
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}
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class TrashBinSet {
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private TypedBin[] binSet = {
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new AluminumBin(),
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new PaperBin(),
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new GlassBin(),
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new CardboardBin()
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};
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public void sortIntoBins(ArrayList bin) {
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for(Object aBin : bin) {
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TypedBinMember t = (TypedBinMember)aBin;
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if(!t.addToBin(binSet))
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System.err.println("Couldn't add " + t);
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}
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}
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public TypedBin[] binSet() { return binSet; }
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}
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public class DoubleDispatch {
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public static void main(String[] args) {
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ArrayList<Trash> bin = new ArrayList<>();
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TrashBinSet bins = new TrashBinSet();
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// ParseTrash still works, without changes:
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ParseTrash.fillBin("DDTrash.dat", bin);
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// Sort from the master bin into the
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// individually-typed bins:
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bins.sortIntoBins(bin);
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// Perform sumValue for each bin...
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for(TypedBin tb1 : bins.binSet())
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Trash.sumValue(tb1.v);
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// ... and for the master bin
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Trash.sumValue(bin);
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}
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} ///:~
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