In the words of the web report submitter:

A DESCRIPTION OF THE REQUEST :
A mis-feature in ArrayList results in un-inlinable get/set methods (among others). The methods are implemented as follows:

    private void RangeCheck(int index) {
        if (index >= size)
            throw new IndexOutOfBoundsException(
                "Index: "+index+", Size: "+size);
    }

    public Object get(int index) {
        RangeCheck(index);
        return elementData[index];
    }

    public Object set(int index, Object element) {
        RangeCheck(index);
        Object oldValue = elementData[index];
        elementData[index] = element;
        return oldValue;
    }


This is pretty amazingly bad code. The goal of RangeCheck is to move the exception-throwing out of the get and set methods, which I suppose was intended to make them inlineable. Indeed, though get() is 12 bytes long (and could be inlined) and set() is 21 bytes long (and also could be inlined), they both MUST STILL CALL RangeCheck, which is 48 bytes long and too large to inline. Thus EVERY get() and set() method call must STILL result in a full method call overhead.


JUSTIFICATION :
My fix below is over 4 times faster in my tests!

I've not delved deeply into the java.util.* code, but if this one was so easy to find, I shudder to think about how poorly the rest of the code has been written with regard to efficiency. java.util.* is central to Java, and a small amount of work rejiggering it could result in major efficiency improvements to the system as a whole.


CUSTOMER SUBMITTED WORKAROUND :

A trivial modification of get() and set() fixes this quite handily:

    public Object get(int index) {
        if (index >= size) RangeCheck(index);
        return elementData[index];
    }

    public Object set(int index, Object element) {
        if (index >= size) RangeCheck(index);
        Object oldValue = elementData[index];
        elementData[index] = element;
        return oldValue;
    }


Now RangeCheck is ONLY CALLED if we're out of bounds, a rare condition. get() is 19 bytes and set(...) is 29 bytes, both inlinable.

(Incident Review ID: 311065)