rt.jar中的工厂设计模式实现

Question

I was reading factory design pattern and on one of the links I read the below mentioned fact.

{ Factory pattern which is used along with various Immutable classes likes Boolean eg Boolean.valueOf() }

With this the background, can some one explain how it has been implemented in Boolean and other immutable classes. Apologies if I am missing a silly thing here.

Regards Tarun

Answer 1

If you see two methods below :

public static Boolean valueOf(boolean b) {
    return (b ? TRUE : FALSE);
}

public static Boolean valueOf(String s) {
    return toBoolean(s) ? TRUE : FALSE;
}

These are static methods of Boolean class and return Boolean type object based on parameter that is provided.

So, you don't create Boolean object, instead Boolean class itself creates/returns(already created) object for you. Hence factory for you.

Answer 2

它不会返回一个new Boolean() ，而是检查参数并返回一个现有的Boolean对象， Boolean.TRUE或Boolean.FALSE 。