Returns the number of instances currently idle in this pool. This may be
considered an approximation of the number of objects that can be
{@link #borrowObject borrowed} without creating any new instances.
Returns a negative value if this information is not available.
@return the number of instances currently idle in this pool.
Returns the number of instances currently idle in this pool. This may be considered an approximation of the number of objects that can be {@link #borrowObject borrowed} without creating any new instances. Returns a negative value if this information is not available. @return the number of instances currently idle in this pool.