CODEWITHSUNDEEP
javaloopsvariables
Noor Eldali
Noor Eldali

Reputation: 29

How is declaring a new variable inside a loop NOT giving errors?

I'm new to android and currently learning the basics. the code below is meant to display a list of numbers (1-10). I want to understand why the code runs with no errors in android studio and it actually displays the list. From what I see, we are declaring the variable wordView multiple times without changing the variable name. Are we updating the same WordView variable each time? if so, how am I getting a list?

LinearLayout rootView = (LinearLayout) findViewById(R.id.rootView);
    int index = 0;
    while (index < 10) {
        TextView wordView = new TextView(this);
        wordView.setText(words.get(index));
        rootView.addView(wordView);
        index ++;

    }

Upvotes: 2

Views: 85

Answers (3)

user7159857
user7159857

Reputation:

Declaring a variable inside a loop makes the variable only available in the scope of that instance in the loop. Basically, each iteration of the loop, the variable gets created and goes out of scope (is "forgotten") at the end of the iterations.

Upvotes: 2

Santanu Sur
Santanu Sur

Reputation: 11477

You can gracefully define a variable within a loop the scope of the variable is only till each iteration. In each iteration a new object of type TextView is created but

Remember

you cannot declare a variable within if statement

   if (index < 10) {
        TextView wordView = new TextView(this);
        wordView.setText(words.get(index)); // this will throw compile time error..

        }

Upvotes: 1

Suresh Atta
Suresh Atta

Reputation: 121998

Scope matters.

In each iteration a new Object of TextView gets created and died in the same iteration as the scope ends there in the same iteration.

while (index < 10) {
        TextView wordView = new TextView(this);
        wordView.setText(words.get(index));
        rootView.addView(wordView);
        index ++;

    }

Variable wordView gets created and ends in the same iteration.

while (index < 10) {
        TextView wordView = new TextView(this); // created
        wordView.setText(words.get(index));
        rootView.addView(wordView);
        index ++;
        // died here 
    }

As soon as the scope end, garbage collector catches that instance as there is no reference of it anymore.

Upvotes: 1

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