95 lines
2.5 KiB
Java
95 lines
2.5 KiB
Java
// generics/Fill2.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://mindviewinc.com/Books/OnJava/ for more book information.
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// Using adapters to simulate latent typing.
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// {main: Fill2Test}
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import generics.coffee.*;
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import java.util.*;
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import java.util.function.*;
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interface Addable<T> { void add(T t); }
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public class Fill2 {
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// Classtoken version:
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public static <T> void fill(Addable<T> addable,
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Class<? extends T> classToken, int size) {
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for(int i = 0; i < size; i++)
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try {
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addable.add(classToken.newInstance());
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} catch(InstantiationException |
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IllegalAccessException e) {
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throw new RuntimeException(e);
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}
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}
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// Supplier version:
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public static <T> void fill(Addable<T> addable,
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Supplier<T> generator, int size) {
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for(int i = 0; i < size; i++)
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addable.add(generator.get());
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}
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}
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// To adapt a base type, you must use composition.
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// Make any Collection Addable using composition:
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class AddableCollectionAdapter<T> implements Addable<T> {
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private Collection<T> c;
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public AddableCollectionAdapter(Collection<T> c) {
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this.c = c;
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}
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@Override
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public void add(T item) { c.add(item); }
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}
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// A Helper to capture the type automatically:
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class Adapter {
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public static <T>
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Addable<T> collectionAdapter(Collection<T> c) {
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return new AddableCollectionAdapter<>(c);
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}
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}
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// To adapt a specific type, you can use inheritance.
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// Make a SimpleQueue Addable using inheritance:
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class AddableSimpleQueue<T>
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extends SimpleQueue<T> implements Addable<T> {
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@Override
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public void add(T item) { super.add(item); }
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}
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class Fill2Test {
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public static void main(String[] args) {
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// Adapt a Collection:
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List<Coffee> carrier = new ArrayList<>();
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Fill2.fill(
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new AddableCollectionAdapter<>(carrier),
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Coffee.class, 3);
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// Helper method captures the type:
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Fill2.fill(Adapter.collectionAdapter(carrier),
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Latte.class, 2);
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for(Coffee c: carrier)
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System.out.println(c);
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System.out.println("----------------------");
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// Use an adapted class:
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AddableSimpleQueue<Coffee> coffeeQueue =
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new AddableSimpleQueue<>();
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Fill2.fill(coffeeQueue, Mocha.class, 4);
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Fill2.fill(coffeeQueue, Latte.class, 1);
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for(Coffee c: coffeeQueue)
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System.out.println(c);
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}
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}
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/* Output:
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Coffee 0
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Coffee 1
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Coffee 2
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Latte 3
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Latte 4
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----------------------
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Mocha 5
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Mocha 6
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Mocha 7
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Mocha 8
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Latte 9
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*/
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