the Builder pattern is a good choice when designing classes whose constructors or static factories would have more than a handful of parameters.
/** * Created by xfyou 2017/5/27 14:41 14:42. * The Builder pattern simulates named optional parameters */ public 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 class Builder { // Required parameters private final int servingSize; private final int servings; // Optional parameters - initialized to default values private int calories = 0; private int fat = 0; private int carbohydrate = 0; private int sodium = 0; public Builder(int servingSize, int servings) { this.servingSize = servingSize; this.servings = servings; } public Builder calories(int val) { this.calories = val; return this; } public Builder carbohydrate(int val) { this.carbohydrate = val; return this; } public Builder sodium(int val) { this.sodium = val; return this; } public NutritionFacts build() { return new NutritionFacts(this); } } public NutritionFacts(Builder builder) { this.calories = builder.calories; this.carbohydrate = builder.carbohydrate; this.fat = builder.fat; this.servings = builder.servings; this.servingSize = builder.servingSize; this.sodium = builder.sodium; } public int getServingSize() { return servingSize; } public int getServings() { return servings; } public int getCalories() { return calories; } public int getFat() { return fat; } public int getSodium() { return sodium; } public int getCarbohydrate() { return carbohydrate; } }
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