Is it bad to declare variables in a loop Java?

But in the name of best coding practice it is recommended to declare the variable in the smallest possible scope (in this example it is inside the loop, as this is the only place where the variable is used). It is the result of the JVM Soecification, not ‘compiler optimization’.

Can I declare a variable inside a loop?

Often the variable that controls a for loop is needed only for the purposes of the loop and is not used elsewhere. When this is the case, it is possible to declare the variable inside the initialization portion of the for.

Is declaring a variable expensive?

It doesn’t matter where the variable was declared, just that it was declared – and it will be allocated onto the stack, regardless. Declaring variables isn’t “expensive,” per se; if it’s easy enough to be not used as a variable, the compiler will probably remove it as a variable.

How do you use a variable outside of a loop?

You have defined the variable outside the loop, so the only thing you need to do is to initialize it, as the error message you should get suggests. String name = “not set”; while(loop) { name = if (condition) // do something to break the loop. } // can use name here.

Can a variable declared within a for-loop still be used after the loop is complete?

Not at all. As long as you don’t save the object’s address past the end of its lifetime, there’s nothing wrong with it. The allocation and deallocation will very often be done on entry to and exit from the function rather than the block, as a performance optimization.

What happens to variable after for loop?

Yes, the variable is created and destroyed N times, unless the compiler optimizes it somehow (which it can, I believe). It’s not a very big deal when you have just one int though.

Should you declare variables at the top?

It’s best to declare variables when you first use them to ensure that they are always initialized to some valid value and that their intended use is always apparent. The alternative is typically to declare all variables in one location, typically at the top of the block or, even worse, at the top of a function.

Can you initialize variables in a for loop?

In Java, multiple variables can be initialized in the initialization block of for loop regardless of whether you use it in the loop or not. Example: Java.

Why do we declare variables inside of a loop?

Declaring variables inside or outside of a loop, It’s the result of JVM specifications But in the name of best coding practice it is recommended to declare the variable in the smallest possible scope (in this example it is inside the loop, as this is the only place where the variable is used). Declaring objects in the smallest scope improve

Is it better to declare STR inside or outside the while loop?

Declaring String str outside of the while loop allows it to be referenced inside & outside the while loop. Declaring String str inside of the while loop allows it to only be referenced inside that while loop. String str; while (condition) { str = calculateStr (); ….. } is NOT better than this:

Is it right to initialize a variable in a loop?

In short, you are right to do it. Note however that the variable is not supposed to retain its valuebetween each loop. In such case, you may need to initialize it every time. You can also create a larger block, encompassing the loop, whose sole purpose is to declare variables which must retain their value from one loop to another.

What is the best practice for incrementing variables outside for-loop?

Google suggests that for time-critical code to declare incrementing variables outside of a for-loop, as if inside the for-loop, it re-declares it each time in that environment. The performance difference is very noticeable for expensive algorithms. – aaroncarsonart Nov 18 ’15 at 6:03