NutritionFacts.java

/**
 * Builder pattern example from Effective Java.
 */
public final class NutritionFacts {
  private final int servingSize;
  private final int servings;
  private final int calories;
  private final int fat;
  private final int sodium;
  private final int carbohydrate;

  public static final class Builder {
    // Required
    private final int servingSize;
    private final int servings;

    // Optional
    private int calories     = 0;
    private int fat          = 0;
    private int sodium       = 0;
    private int carbohydrate = 0;

    public Builder(int servingSize, int servings) {
      this.servingSize = servingSize;
      this.servings    = servings;
    }

    public Builder calories(int val) {
      calories = val;
      return this;
    }

    public Builder fat(int val) {
      fat = val;
      return this;
    }

    public Builder sodium(int val) {
      sodium = val;
      return this;
    }

    public Builder carbohydrate(int val) {
      carbohydrate = val;
      return this;
    }

    public NutritionFacts build() {
      return new NutritionFacts(this);
    }
  }

  private NutritionFacts(Builder builder) {
    servingSize  = builder.servingSize;
    servings     = builder.servings;
    calories     = builder.calories;
    fat          = builder.fat;
    sodium       = builder.sodium;
    carbohydrate = builder.carbohydrate;
  }

  @Override
  public String toString() {
    return "servingSize:  " + servingSize  + "\n" +
           "servings:     " + servings     + "\n" +
           "calories:     " + calories     + "\n" +
           "fat:          " + fat          + "\n" +
           "sodium:       " + sodium       + "\n" +
           "carbohydrate: " + carbohydrate;
  }

  public static void main(final String[] args) {
    NutritionFacts cocoCola = new NutritionFacts.Builder(240, 8).
      calories(100).sodium(35).carbohydrate(27).build();

    System.out.println(cocoCola);
  }
}