Тестовое задание

На я зыке программирования Java, выполнить следующее задание: eneral description
Write a calculator for evaluating arithmetic expressions.
An expression can consist of:
Digits (0-9)
Dots as decimal marks (valid example: 100.02, not valid example : 100..02)
Parentheses
Mathematical symbols (allowed are : "+", "-", "*", "/")
Rounding is to be performed to 4 significant digits, only the final result is to be rounded. Example: 102.12356 -> 102.1236
Input and expected output
Input : String containing arithmetic expression
Output : evaluation result or null if the expression cannot be evaluated
Examples
Calculator c = new CalculatorImpl();
System.out.println(c.evaluate("(1+38)*4-5")); // Result: 151
System.out.println(c.evaluate("7*6/2+8")); // Result: 29
System.out.println(c.evaluate("-12)1//(")); // Result: null