Removing an object in java with only reference to it in an arraylist

Question

I have an arrayList with an custom object:

public ArrayList<Mode> modes = new ArrayList<>();

That list has for example 3 instances in it. How would I set all those instances to be available for the garbage collector to remove them?

for (Mode mode : modes)
    mode = null;

The above does not work. My Eclipse (IDE) just says that the local variable mode is never used. How would I get the actual instance to remove it?

Answer 1

Just clear the ArrayList to remove all the elements.

modes.clear();

Or use its Iterator and remove those you want.

Answer 2

Use the List.set method to set individual elements to null.

for(int i=0;i<modes.size();++i)
    modes.set(i,null);

Use List.clear() to clear the entire array.

Or use an iterator to remove all elements:

Iterator<Mode> it = modes.iterator();
while(it.hasNext())
    it.remove();