OnJava8-Examples/onjava/Suppliers.java
2016-09-23 13:23:35 -06:00

38 lines
1.1 KiB
Java

// onjava/Suppliers.java
// (c)2016 MindView LLC: see Copyright.txt
// 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.*;
import java.util.function.*;
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;
}
}