63 lines
1.4 KiB
Java
63 lines
1.4 KiB
Java
// generics/FactoryConstraint.java
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// (c)2017 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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import java.util.*;
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import java.util.function.*;
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import onjava.*;
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class IntegerFactory implements Supplier<Integer> {
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private int i = 0;
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@Override
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public Integer get() {
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return ++i;
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}
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}
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class Widget {
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private int id;
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Widget(int n) { id = n; }
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@Override
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public String toString() {
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return "Widget " + id;
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}
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public static
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class Factory implements Supplier<Widget> {
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private int i = 0;
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@Override
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public Widget get() { return new Widget(++i); }
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}
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}
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class Fudge {
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private static int count = 1;
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private int n = count++;
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@Override
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public String toString() { return "Fudge " + n; }
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}
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class Foo2<T> {
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private List<T> x = new ArrayList<>();
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Foo2(Supplier<T> factory) {
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Suppliers.fill(x, factory, 5);
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}
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@Override
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public String toString() { return x.toString(); }
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}
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public class FactoryConstraint {
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public static void main(String[] args) {
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System.out.println(
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new Foo2<>(new IntegerFactory()));
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System.out.println(
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new Foo2<>(new Widget.Factory()));
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System.out.println(
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new Foo2<>(Fudge::new));
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}
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}
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/* Output:
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[1, 2, 3, 4, 5]
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[Widget 1, Widget 2, Widget 3, Widget 4, Widget 5]
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[Fudge 1, Fudge 2, Fudge 3, Fudge 4, Fudge 5]
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*/
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