As is said in title
Why is Google's http client faster? I want to know it..
If it's lots of words to explain , give me the link please.
Google HTTP Client is an high-level HTTP abstraction, which allows you to use a pluggable transport library (information taken right from https://code.google.com/p/google-http-java-client/). One those is the Apache HTTP Client, which means you really can't compare the two of them in terms of speed (since they're fundamentally different libraries).
However, since using Google's HTTP Client on top of the Apache HTTP Client introduces overhead (since you add an extra layer), just using Apache's will be faster.