Determine if the requested {@code index} and {@code length} will fit within {@code capacity}.
@param index The starting index.
@param length The length which will be utilized (starting from {@code index}).
@param capacity The capacity that {@code index + length} is allowed to be within.
@return {@code true} if the requested {@code index} and {@code length} will fit within {@code capacity}.
{@code false} if this would result in an index out of bounds exception.
Determine if the requested {@code index} and {@code length} will fit within {@code capacity}. @param index The starting index. @param length The length which will be utilized (starting from {@code index}). @param capacity The capacity that {@code index + length} is allowed to be within. @return {@code true} if the requested {@code index} and {@code length} will fit within {@code capacity}. {@code false} if this would result in an index out of bounds exception.