55 lines
1.4 KiB
Java
55 lines
1.4 KiB
Java
// generics/Fill.java
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// Generalizing the FilledList idea
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// {main: FillTest}
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import java.util.*;
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// Doesn't work with "anything that has an add()." There is
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// no "Addable" interface so we are narrowed to using a
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// Collection. We cannot generalize using generics in
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// this case.
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public class Fill {
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public static <T> void fill(Collection<T> collection,
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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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// Assumes no-arg constructor:
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try {
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collection.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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}
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class Contract {
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private static long counter = 0;
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private final long id = counter++;
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@Override
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public String toString() {
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return getClass().getName() + " " + id;
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}
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}
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class TitleTransfer extends Contract {}
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class FillTest {
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public static void main(String[] args) {
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List<Contract> contracts = new ArrayList<>();
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Fill.fill(contracts, Contract.class, 3);
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Fill.fill(contracts, TitleTransfer.class, 2);
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for(Contract c: contracts)
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System.out.println(c);
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SimpleQueue<Contract> contractQueue =
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new SimpleQueue<>();
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// Won't work. fill() is not generic enough:
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// Fill.fill(contractQueue, Contract.class, 3);
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}
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}
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/* Output:
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Contract 0
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Contract 1
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Contract 2
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TitleTransfer 3
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TitleTransfer 4
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*/
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