Use double for all your calculations and temp variables. Use float when you need to maintain an array of numbers - float[] (if precision is sufficient), and you are dealing with over tens of thousands of float numbers.

Many/most math functions or operators convert/return double, and you don't want to cast the numbers back to float for any intermediate steps.

E.g. If you have an input of 100,000 numbers from a file or a stream and need to sort them, put the numbers in a float[].

Use double for all your calculations and temp variables. Use float when you need to maintain an array of numbers - float[] (if precision is sufficient), and you are dealing with over tens of thousands of float numbers.

Many/most math functions or operators convert/return double, and you don't want to cast the numbers back to float for any intermediate steps.

E.g. If you have an input of 100,000 numbers from a file or a stream and need to sort them, put the numbers in a float[].