I am receiving the following error when I
sudo apt-get install (something)


"
sha256sum mismatch jdk-7u3-linux-x64.tar.gz
Oracle JDK 7 is NOT installed.
dpkg: error processing oracle-java7-installer (--configure):
subprocess installed post-installation script returned error exit status 1
Setting up compiz-plugins (1:0.9.7.8-0ubuntu1.4) ...
Setting up compiz-plugins-main (1:0.9.7.0~bzr19-0ubuntu10) ...
Setting up compizconfig-settings-manager (0.9.5.92-0ubuntu3) ...
Processing triggers for python-central ...
Errors were encountered while processing:
oracle-java7-installer
E: Sub-process /usr/bin/dpkg returned an error code (1)
"


Is there anything to fix this ?

Their maybe something wrong with the source of "something". This implies the software is not the original by the developer. You may want to use different repositories for it.

do you have any idea how can i fix this ?

jdk-7u3-linux-x64.tar.gz can be downloaded from oracle, but I do not really understand how did you try to install it.