在我的 Java 代码中发现奇怪的表达式：变量赋值语法

Question

Somewhere in my code today, I found that I had written the following line

JsonArray environmentJsonArray = new JsonArray(), playerJsonArray, teamJsonArray;

I am at a complete loss in understanding how this is even working. The basic question is, What are the two variables on my RHS ? I checked if I had declared them before, but I did not. The compiler still does not complain apparently indicating that the variables playerJsonArray and teamJsonArray were taken as fresh declarations. But then the declared variables are always on the LHS. Isn't that so? Has something changed in Java's basic syntax? Iam trying to go through the specifications to get to the bottom but just in case anyone has a quicker understanding please.

Answer 1

You're declaring 3 variables of type JsonArray , and only assigning an initial value to the first.

It's basically the same as:

JsonArray environmentJsonArray = new JsonArray();
JsonArray playerJsonArray;
JsonArray teamJsonArray;

The relevant section of JLS 9 is Sec 14.4 .

Has something changed in Java's basic syntax?

It has been like this since version 1.0 .

Answer 2

It's similar to declaring 3 variables whose type is JsonArray also you only initialize the first one which is environmentJsonArray. The remaining ones which are playerJsonArray, teamJsonArray are the uninitialized ones.