How to remove everything from an ArrayList in Java but the first element

Question

I am new to java programming, been programing in php so I\'m used to this type of loop:

int size = mapOverlays.size();
for(int n=1;n

        

Answer 1

I think it would be faster to create a new ArrayList with just the first element inside. something like :

E temp = mapOverlays.get(0);
mapOverlays = new ArrayList<E>().add(temp);

Answer 2

int size = mapOverlays.size();
for(int n=0;n<size;n++)
{
    mapOverlays.remove(n);
}

In java, if mapOverlays is list then it start with 0 as a first index.So n=0 in for loop.

Answer 3

If you are using a java.util.List implementation instead of array, the size of the array gets smaller everytime you remove something and the n+1 item replaces the n item. This code will eventually result to ArrayIndecOutOfBoundsException when n becomes greated than the last index in the list.

Java also has an array type and the size of that one cannot be changed:

Object[] mapOverlay = //initialize the array here
int size = mapOverlay.length;
for(int n=1;n<size;n++)
{
    mapOverlay[n] = null;
}

I don't know PHP but this sounds like it's close to the behavior you are after. However the List implementations are more flexible and comfortable in use than the arrays.

EDIT: Here's a link to the Javadoc of List.remove(int): http://java.sun.com/javase/6/docs/api/java/util/List.html#remove%28int%29

Answer 4

Why don't you try backwards?

int size = itemizedOverlay.size();
for(int n=size-1;n>0;n--)
{
    mapOverlays.remove(n);
}

Answer 5

As I get it, after removal, array keys are rearranged or not? Yes, the item which was on position 2 is on position 1 after you removed the item on position 1.

You can try this:

Object obj = mapOverlays.get(0); // remember first item
mapOverlays.clear(); // clear complete list
mapOverlays.add(obj); // add first item