96 lines
2.8 KiB
Java
96 lines
2.8 KiB
Java
// patterns/doubledispatch/DoubleDispatch.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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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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// {java patterns.doubledispatch.DoubleDispatch}
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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(Aluminum 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(Paper 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(Glass 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(Cardboard 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 List<TypedBin> binSet = Arrays.asList(
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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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@SuppressWarnings("unchecked")
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public void sortIntoBins(List bin) {
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bin.forEach( aBin -> {
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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 List<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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List<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("doubledispatch", 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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bins.binSet().forEach(tb -> Trash.sumValue(tb.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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/* Output: (First and Last 10 Lines)
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Loading patterns.doubledispatch.Glass
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Loading patterns.doubledispatch.Paper
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Loading patterns.doubledispatch.Aluminum
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Loading patterns.doubledispatch.Cardboard
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weight of patterns.doubledispatch.Aluminum = 89.0
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weight of patterns.doubledispatch.Aluminum = 76.0
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weight of patterns.doubledispatch.Aluminum = 25.0
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weight of patterns.doubledispatch.Aluminum = 34.0
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weight of patterns.doubledispatch.Aluminum = 27.0
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weight of patterns.doubledispatch.Aluminum = 18.0
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...________...________...________...________...
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weight of patterns.doubledispatch.Aluminum = 93.0
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weight of patterns.doubledispatch.Glass = 93.0
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weight of patterns.doubledispatch.Paper = 80.0
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weight of patterns.doubledispatch.Glass = 36.0
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weight of patterns.doubledispatch.Glass = 12.0
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weight of patterns.doubledispatch.Glass = 60.0
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weight of patterns.doubledispatch.Paper = 66.0
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weight of patterns.doubledispatch.Aluminum = 36.0
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weight of patterns.doubledispatch.Cardboard = 22.0
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Total value = 1086.0599818825722
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*/
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