In Physics, Interference of light is in accordance with the principle of conservation of energy. But, in some text i found that diffraction doesn’t obey, even though both are wave phenomenon. If it is so, what is the reason behind it.

(may be broke/outdated!)
In Physics, Interference of light is in accordance with the principle of conservation of energy. But, in some text i found that diffraction doesn’t obey, even though both are wave phenomenon. If it is so, what is the reason behind it.