OnJava8-Examples/onjava/Suppliers.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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// onjava/Suppliers.java

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// A utility to use with Suppliers

package onjava;

import java.util.*;

import java.util.function.*;

import java.util.stream.*;

public class Suppliers {

// Create a collection and fill it:

public static <T, C extends Collection<T>> C

create(Supplier<C> factory, Supplier<T> gen, int n) {

return Stream.generate(gen)

.limit(n)

.collect(factory, C::add, C::addAll);

}

// Fill an existing collection:

public static <T, C extends Collection<T>>

C fill(C coll, Supplier<T> gen, int n) {

Stream.generate(gen)

.limit(n)

.forEach(coll::add);

return coll;

}

// Use an unbound method reference to

// produce a more general method:

public static <H, A> H fill(H holder,

BiConsumer<H, A> adder, Supplier<A> gen, int n) {

Stream.generate(gen)

.limit(n)

.forEach(a -> adder.accept(holder, a));

return holder;

}