Effective Java Second Edition --- Builder Pattern

如果类的构造器或者静态工厂中有多个参数，设计这种类时，Builder模式是一种不错的选择，特别是当大多数参数是可选的时候。

与使用传统的重载构造函数模式相比，使用Builder模式的客户端代码更易于阅读和编写，构造器也比javabeens更加安全。

代码如下：

/**
* Created by zhanga.fnst on 2016/3/14.
*/
public class NutritionFacts {
private final int servingSize;
private final int servings;
private final int calories;
private final int flat;
private final int sodium;
private final int carbohydrate;

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

//Optional parameters
private  int calories = 0;
private  int flat = 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 flat(int val){
flat = val;
return this;
}

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

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

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

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

View Code
main方法：

/**
* Created by zhanga.fnst on 2016/3/14.
*/
public class TestMain {
NutritionFacts cocaCola = new NutritionFacts.Builder(240,8).
calories(100).sodium(35).carbohydrate(27).build();
}