NIO has significant impact on HTTP Servers not on stand alone single instance clients.
This is true for the asynchronous network IO parts of NIO, but definitely not all of it. It also enables memory mapping and DMA, two things that can have significant impact on stand alone software.
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NIO has significant impact on HTTP Servers not on stand alone single instance clients.
The only time you'd use a NIO client, is on a server - for example, when building a caching proxy server.
The expected benefits are higher throughput of the proxy (lower CPU/RAM consumption allows multiple clients to operate in parallel).
Individual downloads being faster was never expected to be a benefit
This is true for the asynchronous network IO parts of NIO, but definitely not all of it. It also enables memory mapping and DMA, two things that can have significant impact on stand alone software.