java - 新对象是否创建？

Question

我正在阅读 Joshua Bloch 的Effective Java。第 1 项让我感到困惑，它指出

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？

//constructor
Orange(){
}

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

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

Orange orange=new Orange();

Orange orange=Orange.staticFactoryMethod();

Answer 1

静态工厂并不总是需要创建新对象。你可以这样:

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

但是你也可以有类似的东西

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