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javaandroidfor-loopforeach
Dr. Ehsan Ali
Dr. Ehsan Ali

Reputation: 4884

How to change from for to foreach in this case?

In my Android App I have simple C-like 'for loops' like this:

for (int i = 0; i < max_count; i++) {
  // I must use the value of 'i' in the for loop body

}

But the Android studio gives me a Lint warning, suggesting to change the for loop to a foreach loop.

Can you tell me how can I switch to foreach loop and use 'i' variable in the body of the loop?

Upvotes: 4

Views: 2129

Answers (3)

Ash
Ash

Reputation: 21

If you're iterating over an array, the foreach construct means you do not need an array index.

So, for example:

int[] myArrayValues = new int[4];

// code to fill up array ...

for (int specificValue : myArrayValues) {
    // specific value is a value from the array, do something useful with it
}

In this case, specificValue is equal to myArrayValues[0] on the first iteration through the loop, then myArrayValues[1], myArrayValues[2] and finally myArrayValues[3] as the loop iterates.

Notes that in the answer above, although there is a variable i, it's not an index at all and will contain the vales in the array (in that case, they're all 0 until the array is filled with values).

So, for example to sum the values in the array, we can do something like this:

int[] items = new int[3];
items[0] = 3;
items[1] = 6;
items[2] = 7;

int sum = 0;

for( int value : items ) {
    sum += value;
}

// at this point sum = 16

Think of it as "for each value in items"

Upvotes: 1

Sergey Shustikov
Sergey Shustikov

Reputation: 15821

foreach construction is not applicable to int.

foreach works only with arrays and collections.

For alternative you can use :

int max = 5;
int[] arr = new int[max];

for (int i : arr) {

}

Docs :

The enhanced for-loop is a popular feature introduced with the Java SE platform in version 5.0. Its simple structure allows one to simplify code by presenting for-loops that visit each element of an array/collection without explicitly expressing how one goes from element to element.

Upvotes: 4

Chris Sprague
Chris Sprague

Reputation: 740

If you have to make use of the counter variable within the loop, it doesn't make sense to switch to using a for each -- essentially, the linter may be wrong here.

If you do want to change it nevertheless, you need to define the counter outside the for each as follows:

int i = 0; // your counter, now defined outside of the loop -- but still usable inside
for ( SomeItem e : SomeIterableObj ) { // the for-each loop
    // do something with the element, 'e'
    // do something with the counter, 'i'
    i++; // or manipulate the counter in whichever way you need to.
}

This way, you're using a for each loop and you still get to make use of a counter.

Upvotes: 3

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