Files that you download from the Oracle website have a number next to them with the "cksum" label. This number is used to verify that you have downloaded the exact file as it exists on the Oracle website. So if you are unsure that your download completed successfully you can check the file yourself and be sure that you got the file ok.

The cksum command is native on Linux, but to use it on Windows you can download gnuwin32, which will also give your machine a load of other useful Linux utilities like cat, tr, etc.