是否创建了新对象? [英] new object is created or not?

问题描述

我正在阅读 Joshua Bloch 的Effective Java.它在第 1 项中让我感到困惑

I am reading Effective Java by Joshua Bloch. It confuses me in the item 1, where it states

静态工厂方法的第二个优点是，与构造函数不同，它们不需要在每次调用时都创建一个新对象.

A second advantage of static factory method is that, unlike constructors, they are not required to create a new object each time time they're invoked.

静态工厂方法不是每次调用时都会创建一个新对象吗?

Isn't the static factory method meant to create a new object each time it is invoked?

//constructor
Orange(){
}

//static factory method
static Orange staticFactoryMethod(){
    return new Orange;
}

不会调用构造函数或 staticFactoryMethod 来创建 Orange 的实例吗?

Won't calling either the constructor or the staticFactoryMethod create an instance of Orange?

Orange orange=new Orange();

Orange orange=Orange.staticFactoryMethod();

推荐答案

静态工厂并不总是需要创建新对象.你可以有这个:

A static factory does not always need to create a new object. You can have this:

static Orange staticFactoryMethod(){
    return new Orange();
}

但你也可以有类似的东西

But you can also have something like

static Orange staticFactoryMethod(){
    Orange o = ... //find an orange in a basket of available oranges that has been already initialized
    return o;
}

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