Java并发性主题：对象或其内部状态的发布

Question

I'm reading the code base of a project, and here's some code I can't under stand:

protected BaseApiCommand(String apiName, ApiParams params, boolean isGetRequest) {
    this.apiName = apiName;
    this.apiParams = params;
    this.isGet = isGetRequest;
    if (apiParams == null) {
        apiParams = new ApiParams();
    }
}

public static BaseApiCommand createCommand(String apiName, boolean isGet, ApiParams params) {
    return new BaseApiCommand(apiName, params, isGet);
}

I know it's about publication, but I just can't understand why it's unsafe otherwise to expose the constructor directly. Can anyone explain it in detail ?

Answer 1

In fact the static function is a static factory method to the class, as proposed by Joshua Bloch in Effective Java. This is a very common pattern in Java language and protects the constructor from the class consumers.