Julius Caesar, a play written by William Shakespeare, does not show very good friendship. The saying "Keep your friends close but your enemies closer" applies undoubtedly to the play.
Within the play, Brutus was persuaded, quite easily actually, to help in the conspiracy against Julius Caesar. Brutus was a beloved friend of Caesar's, yet he did not care to kill his friend. Brutus believed that the murder of Caesar was the best course of action he could take in protecting his country. He believed that Caesar had become too ambitious. Brutus became full of guilt from what he had done though. Brutus could finally withstand his conscience no more, and he killed himself.
Cassius was different though. He would be kind to people, but later he would begin to tare them down. Cassius did not care much for friendship, he just wanted power.
Julius Caesar was all too trustworthy of his 'friends'. He believed that all the other politicians were his friends, but they conspired against him and killed him. Caesar thought that he had loyal trustworthy friends, but he did not look close enough to tell that they were all frauds.
In the end, people do not need to decide so quickly who their friends are that they do not truly see them. A 'friend' could quickly turn around and stab them in the back.