如何将日期（yyyy-mm-dd）转换为int变量？

i want to change date with my formulation (in java code in android studio) to another date, but i need date (yyyy-mm-dd) at int variable to use my formulates on it(f.example i want a=yyyy/2 , b= mm+3, c= dd-25 and result for new date is: aaaa/bb/cc), help me to solve that?i want to change date with my formulation (in j