Recently wrote a feature point, with the variable parameters in Java, really made me sad case. .
What is a variable parameter?
The method parameters is Object... argsthree points form a plurality of parameters may be received parameters.
The actual code is not a quote, look at it this example:
Example 1
public static void main(String[] args) {
test("name=%s&memo=%s", "Java技术栈", "666");
}
private static void test(String text, Object... params) {
String result = String.format(text, params);
System.out.println(result);
}
Guess what the result is? The results we imagine:
name=Java技术栈&memo=666
Example 2
public static void main(String[] args) {
test("name=%s&memo=%s", "Java技术栈");
}
private static void test(String text, Object... params) {
String result = String.format(text, params, "666");
System.out.println(result);
}
I put "666" moved to the inside of the sub-way into the final format, and then look at what the results are.
name=[Ljava.lang.Object;@4cb2c100&memo=666
This is not the result I wanted, the variable parameter array params object address as the output value came out, made me sad case, I finally get rid of the variable parameters. .
JDK there are many useful to variable parameters, the actual development can not recommend the use of a variable reference, it brings problems and potential problems will be far greater than the convenience, such as reconstruction method, updating, or other will bring to a lot of problems.
About variable parameters, there is also the development of standardized, you can not just write. I found Ali Baba "Java Development Manual" Statute on variable parameters.
Type the same parameters, same business meaning, can use Java variable parameters, avoid the use of Object.
Description: Variable parameters must be placed at the end of the argument list. (Do not try to promote the students variable parameter programming)
正例： public List<User> listUsers(String type, Long... ids) {...}
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Alibaba is also not recommended for everyone to cooperate variable parameters, we can see that it brings there will be more pit pit. .
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