How to rewrite Android (Java) program to an equivalent Swift code and run it on iOS

Answer 1

swift syntax is similar to Java, but maybe it have difference method.
iOs and Android have a difference sdk, that mean the API will be difference, you should learn both of them, porting it is not easy.

Answer 2

to switch a code from one language to another you must :
_ know the language of the source code well
_understand the algorithm of the program
_understand the language u want to covert the code to

Answer 3

Know your codes architecture and control flow, as well as the constructs in either language that will get you there.