多種方法,我發現調用Java的多種方法中的一種新的方式,我真的不明白髮生了什麼事背後:調用Java中
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)
{ 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; }
public NutritionFacts build() {
return new NutritionFacts(this);
}
}
private NutritionFacts(Builder builder) {
servingSize = builder.servingSize;
servings = builder.servings;
calories = builder.calories;
}
}
現在的類實例化使用這一行,這裏就是它得到混淆:
NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8).calories(100).sodium(35).carbohydrate(27).build();
這一切都有道理,直到NutritionFacts.Build(int,int),在那之後,究竟發生了什麼?爲什麼Builder類中的calories
,sodium
,carbohydrate
方法需要返回this
?那個班級的地址在哪裏?
謝謝!
這是否意味着從foo.calories返回值(12),這是實例,用於調用線下一種方法,在我們的例子中,鈉(35)? –
@ Cookie503絕對:) –
@ Cookie503沒錯。 –