Check if all items in a list are set to the same boolean value

Question

I have an ArrayList which is populated by a random number of GameObj instances each time the program is run.

If an object makes contact with another object in the ArrayList, it will set a boolean called visible from true to false.

Is there a way to check if all of the item instances in the ArrayList have been set to false through:

XXXX.visible = false

Once I can check if they are all set to false.

Answer 1

You can use Stream.noneMatch() to do this:

if (bricks.stream().noneMatch(GameObj::isVisible)) {
    doStuffIfAllBricksAreInvisible();
}

This returns true, if all bricks are invisible.

Additionally I would recommend to take a look at Stream.allMatch(), which returns true, if all elements of the list match the given predicate.

Using allMatch() this would look like this:

if (bricks.stream().allMatch(b -> !b.isVisible())) {
    doStuffIfAllBricksAreInvisible();
}

To complete this, you also can take a look at Stream.anyMatch(), which returns true, if one of the elements matches the given predicate.

Answer 2

If you are using Java <8, one way will be to store the arraylist size on intialisation in a variable( say variable name be count).

On change of flag from true to false, decrease the count by 1. If flag is already false, do nothing. Now you can just check the count is 0 or not.

If count is 0, print "Well done, Game over" or else continue the game.

For Java 8 or up, you can go for streams API as suggested in other answers.