37 lines
1.0 KiB
Java
37 lines
1.0 KiB
Java
// onjava/Suppliers.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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// A utility to use with Suppliers
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package onjava;
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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public class Suppliers {
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// Create a collection and fill it:
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public static <T, C extends Collection<T>> C
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create(Supplier<C> factory, Supplier<T> gen, int n) {
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return Stream.generate(gen)
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.limit(n)
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.collect(factory, C::add, C::addAll);
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}
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// Fill an existing collection:
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public static <T, C extends Collection<T>>
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C fill(C coll, Supplier<T> gen, int n) {
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Stream.generate(gen)
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.limit(n)
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.forEach(coll::add);
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return coll;
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}
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// Use an unbound method reference to
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// produce a more general method:
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public static <H, A> H fill(H holder,
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BiConsumer<H, A> adder, Supplier<A> gen, int n) {
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Stream.generate(gen)
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.limit(n)
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.forEach(a -> adder.accept(holder, a));
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return holder;
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}
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}
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