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javaarraysfor-loop
Teneff
Teneff

Reputation: 32158

Java for each loop iterate boolean array

I have a boolean array

boolean[] test = {
    false,
    true,
    true,
    false,
    true
};

and I'm trying to flip (true to false, and false to true) the values with "for-each" statement like so:

for(boolean x : test) {
    x = !x;
}

But it's only changing the x variable in the local scope.

I'm new to Java and I want to ask how this could be done and if this is the right approach. I've searched a lot, but most of the examples are used to collect data from the array without modifying it.

Upvotes: 1

Views: 10672

Answers (6)

Ravi Bhatt
Ravi Bhatt

Reputation: 3163

No surprises that it does not work. You are manipulating a local variable after all and its not an object and not a reference. Use a normal for loop and modify corresponding position.

Upvotes: 1

Brent Worden
Brent Worden

Reputation: 10974

You will need to use a non-enhanced for loop if you want affect the values of test:

for (int i = 0; i < test.length; ++i) {
  test[i] = !test[i];
}

Upvotes: 2

Luciano
Luciano

Reputation: 8582

You don't do that with a for each, as the for each reads the value of the array, and stores it in a local variable, as you said. You need to iterate the array and access the index directly. I won't post any code so you can find and think about it.

Upvotes: 1

Luminously
Luminously

Reputation: 299

The enhanced for loop is creating a new variable x and setting the value locally each time because boolean is a primitive and is therefore not passed by reference. For this, you will need to use the old for loop.

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1500225

No, that's not the right approach. The enhanced for loop doesn't let you change the values of what you're iterating over. To invert the array, you'd want to use a regular for loop:

for (int i = 0; i < test.length; i++) {
    test[i] = !test[i];
}

(Note that the enhanced for loop would let you make changes to the objects which any array elements referred to, if they were classes - but that's not the same thing as changing the value of the element itself.)

Upvotes: 9

Bala R
Bala R

Reputation: 108947

You cannot change the item in a for-each loop. Can you use a regular loop instead?

for (int i=0; i < test.length; i++)
{
    test[i] = !test[i];
}

Upvotes: 1

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