When it comes to which java to use, Hadoop is a bit picky. It prefers the Oracle jdk. See the list of apache tested JDKs.

Lately all the google references which use wget or curl are broken.

Silent install

For the impatient here is the one-liner.

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curl -LO 'http://download.oracle.com/otn-pub/java/jdk/7u51-b13/jdk-7u51-linux-x64.rpm' \
-H 'Cookie: oraclelicense=accept-securebackup-cookie'
rpm -i jdk-7u51-linux-x64.rpm

or if you really want it in one single line

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curl -LO 'http://download.oracle.com/otn-pub/java/jdk/7u51-b13/jdk-7u51-linux-x64.rpm' -H 'Cookie: oraclelicense=accept-securebackup-cookie' && rpm -i jdk-7u51-linux-x64.rpm

tl;dr

What I did was: - opened Chrome Developer Toolbar - went to the official oracle download page - clicked Accept License Agreement - clicked on jdk-7u51-linux-x64.rpm - as the download has started, I switched to the Network tab of the Developer Toolbar, and right-clicked on the rpm, and choos Copy as cURL

Voila! Of cours it was a huge line, but it can be trimmed down to just one singe required cookie: oraclelicense=accept-securebackup-cookie

Meanwhile it appeared on stackowerflow with a fatty +50 reputation bounty.