// onjava/FillMap.java
// (c)2017 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.
package onjava;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class FillMap {
  public static <K, V> Map<K,V>
  basic(Supplier<Pair<K,V>> pairGen, int size) {
    return Stream.generate(pairGen)
      .limit(size)
      .collect(Collectors
        .toMap(Pair::key, Pair::value));
  }
  public static <K, V> Map<K,V>
  basic(Supplier<K> keyGen,
        Supplier<V> valueGen, int size) {
    return Stream.generate(
      () -> Pair.make(keyGen.get(), valueGen.get()))
      .limit(size)
      .collect(Collectors
        .toMap(Pair::key, Pair::value));
  }
  public static <K, V, M extends Map<K,V>>
  M create(Supplier<K> keyGen,
           Supplier<V> valueGen,
           Supplier<M> mapSupplier, int size) {
    return Stream.generate( () ->
      Pair.make(keyGen.get(), valueGen.get()))
        .limit(size)
        .collect(Collectors
          .toMap(Pair::key, Pair::value,
                 (k, v) -> k, mapSupplier));
  }
}