How can a Blackhole have mass?

It is said that in Blackhole 100% part of the mass is getting converted into energy. Then how come Blackhole is having mass ?

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They maybe doing so but if you know their mass is inversely proportional to the amount of radiation they emit. So, for a black hole to be of zero mass it will have to emit radiation for a fairly large amount of time. See Hawking Radiation –  Yashbhatt Apr 30 at 15:52
In gravitational terms mass and energy are similar - see special relativity for E=mc^2 etc. Perhaps you could reframe your question? –  adrianmcmenamin Apr 30 at 22:27