Example of using HashMap in Java.

Main.java

import java.util.Arrays;
import java.util.HashMap;

class Ingredient {
  public final String name;

  public Ingredient(String name) {
    this.name = name;
  }

  @Override
  public int hashCode() {
    return name.hashCode();
  }

  @Override
  public boolean equals(Object other) {
    if (other instanceof Ingredient) {
      return name.equals(((Ingredient) other).name);
    }
    return false;
  }

  @Override
  public String toString() {
    return name;
  }
}

class Recipe {
  private Ingredient[] ingredients;

  public Recipe(Ingredient[] ingredients) {
    this.ingredients = ingredients;
  }

  public Ingredient[] getIngredients() {
    return Arrays.copyOf(ingredients, ingredients.length);
  }
}

class Main {
  public static HashMap<Ingredient, Integer> generateDict(Recipe recipe) {
    HashMap<Ingredient, Integer> map = new HashMap<>();

    for (Ingredient ingredient : recipe.getIngredients()) {
      map.putIfAbsent(ingredient, 0);
      int count = map.get(ingredient);
      map.put(ingredient, count + 1);
    }

    return map;
  }

  public static void main(String[] args) {
    HashMap<Ingredient, Integer> map = generateDict(new Recipe(new Ingredient[] {
      new Ingredient("apple"),
      new Ingredient("apple"),
      new Ingredient("butter"),
      new Ingredient("cinnamon"),
      new Ingredient("icing sugar"),
    }));

    System.out.println(map);
  }
}