Java 中的可选方法参数
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Optional method parameter in Java
提问by Shaonline
I have this function httpGet()which calls http():
我有这个函数httpGet()调用http()：
public static int httpGet(String url, StringBuilder response) throws IOException {
return http(url,(http)->http.setRequestMethod("GET"), response);
}
private static int http(String url, httpMethod method, StringBuilder response) throws IOException {
HttpURLConnection http = (HttpURLConnection)new URL(url).openConnection();
http.setConnectTimeout(5000);
http.setReadTimeout(5000);
method.doMethod(http);
int status = 404;
......
......
return status;
}
I want to add an additional parameter for readTimeout, which needs to be optional with a default value that will be used otherwise.
我想添加一个额外的参数 for readTimeout，它需要是可选的，默认值将在其他情况下使用。
In this case readTimeoutis set to 5000 for all the calls, but I want this specific call to be executed for longer timeouts.
在这种情况下readTimeout，所有调用都设置为 5000，但我希望在更长的超时时间内执行此特定调用。
I think I need this new parameter to be optional as I don't want to change the implementations where this http()method has been called.
我想我需要这个新参数是可选的，因为我不想更改http()调用此方法的实现。
This is how I call it:
我是这样称呼它的：
Assert.assertEquals(HTTP_OK, httpGet(DEFAULT_BROWSCAP_ENDPOINT, result));
How can I implement a new optional parameter for readTimeout?
如何为 实现新的可选参数readTimeout？
采纳答案by IceArdor
Java doesn't have default values like Python, C++, VBA, Delphi, and many languages. Create new constructors with the alternate signature.
Java 没有像 Python、C++、VBA、Delphi 和许多语言那样的默认值。使用备用签名创建新的构造函数。
public static int httpGet(String url, StringBuilder response) throws IOException {
return httpGet(URL, response, 5000)
}
public static int httpGet(String url, StringBuilder response, int readTimeout) throws IOException {
return http(url,(http)->http.setRequestMethod("GET"), response, readTimeout);
}
private static int http(String url, httpMethod method, StringBuilder response) throws IOException {
return http(url, method, response, 5000);
}
private static int http(String url, httpMethod method, StringBuilder response, int readTimeout) throws IOException {
HttpURLConnection http = (HttpURLConnection)new URL(url).openConnection();
http.setConnectTimeout(5000);
http.setReadTimeout(readTimeout;
method.doMethod(http);
int status = 404;
......
......
return status;
}
回答by sdabet
You need to create 2 versions of the httpGetmethod (one with the readTimeoutparameter, and another one without it which will call the first version with a default value):
您需要创建该httpGet方法的2 个版本（一个带有readTimeout参数，另一个没有它，它将使用默认值调用第一个版本）：
private static final long DEFAULT_READ_TIMEOUT = 5000;
public static int httpGet(String url, StringBuilder response) throws IOException {
return httpGet(url, response, DEFAULT_READ_TIMEOUT);
}
public static int httpGet(String url, StringBuilder response, long readTimeout) throws IOException {
return http(url,(http)->http.setRequestMethod("GET"), response, readTimeout);
}
private static int http(String url, httpMethod method, StringBuilder response, long readTimeout) throws IOException {
HttpURLConnection http = (HttpURLConnection)new URL(url).openConnection();
http.setConnectTimeout(5000);
http.setReadTimeout(readTimeout);
method.doMethod(http);
int status = 404;
......
......
return status;
}
Now you can decide to provide the timeout
现在您可以决定提供超时
httpGet(DEFAULT_BROWSCAP_ENDPOINT, result, mytimeout)
or not
或不
httpGet(DEFAULT_BROWSCAP_ENDPOINT, result)
回答by Parker Hoyes
Generally the way this is done is by providing many different functions with different signatures that just assume a default value. This can be done by "chaining" a bunch of functions together, each specifying it's default value and calling the more detailed function. For example:
通常，这样做的方法是提供许多具有不同签名的不同函数，这些函数仅采用默认值。这可以通过将一堆函数“链接”在一起来完成，每个函数指定它的默认值并调用更详细的函数。例如：
public void myFunctionWithALotOfArguments(int a, int b, int c, int d) {
// do stuff
}
public void myFunctionWithLessArguments(int a, int b, int c) {
myFunctionWithALotOfArguments(a, b, c, 50);
}
public void myFunctionWithFewArguments(int a, int b) {
myFunctionWithLessArguments(a, b, 25);
}
public void mySimplifiedFunction(int a) {
myFunctionWithFewArguments(a, 9);
}
public void justGuessWhatToDo() {
mySimplifiedFunction(42);
}
