package pattern.builder; public class BuilderDemo { public static void main(String[] args) { NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8) .calories(100).sodium(35).carbohydrate(27).build(); System.out.println(cocaCola); } } /** * 建造者模式 * 1.构造函数参数很多的时候,要创建一个对象非常的麻烦。因为对每个参数赋值的顺序很容易出错。 * 2.使用本模式可以避免冗长的setter调用 * * 关键: * 1.必须的参数仍通过Builder构造方法传入 * 2.可选参数则通过"链式调用"进行设置 * 3.所有需要的属性设置完成后,调用build()方法返回最终的对象 */ // Builder Pattern 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) { calories = val; return this; } public Builder fat(int val) { fat = val; return this; } public Builder carbohydrate(int val) { carbohydrate = val; return this; } public Builder sodium(int val) { sodium = val; return this; } //last step: use Builder's attribute to create the instance! 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 "NutritionFacts [servingSize=" + servingSize + ", servings=" + servings + ", calories=" + calories + ", fat=" + fat + ", sodium=" + sodium + ", carbohydrate=" + carbohydrate + "]"; } }
【设计模式】建造者
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转载自just2learn.iteye.com/blog/2096879
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