应该在哪里声明变量？

Question

I have a complicated condition inside else block inside a loop. So I decided to form some new variables to simplify this condition. Where should I declare these variables?

//here 1
for (...) {
   //here 2
   if(...) {

   } else {
      //here 3
      if (cond1 && cond2){}
   }
} 

Answer 1

You should declare variables closest as possible to their usages, and in the "smallest" scope possible.

In your example, if cond1,cond2 are used ONLY when you write them in the sample, they should be declared in here 3 .

Answer 2

您应该在需要的地方声明变量，因此在这种情况下，可能在here 3 。

Answer 3

Probably the best solution is this :

 boolean cond1,cond2 = false;
    for (...) {
       //here 2
       if(...) {

       } else {
          cond1 = ...
          cond2 = ...
          if (cond1 && cond2){}
       }
    } 

this allows you to allocate no memory for variables at each iteration.