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Calculator.java
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Calculator.java
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package task;
import java.util.Stack;
import task.operations.Operation;
import task.operations.OprationFactory;
/**
* A class that implements methods for calculating the value of an arithmetic expression.
*/
public class Calculator {
public static double zeroValue = 0.000000001;
/**
* Method-helper to determine operator.
*
* @param elem parsed token.
* @return true if this is an operator.
*/
private static boolean isOperator(String elem) {
String ops = "sin cos log pow sqrt + - * /";
if (ops.indexOf(elem) != -1) {
return true;
}
return false;
}
/**
* Static method realises calculating.
*
* @param in input string of expression.
* @return result of expression if possible.
*/
public static double calculate(String input) {
String[] substrings = input.split(" ");
Stack<Double> stack = new Stack<>();
for (int i = substrings.length - 1; i >= 0; i--) {
if (isOperator(substrings[i])) {
Operation op = OprationFactory.create(substrings[i]);
stack.push(op.apply(stack));
} else {
try {
stack.push(Double.parseDouble(substrings[i]));
} catch (NumberFormatException e) {
throw new CalculationException("Incorrect or non-existent operator!");
}
}
}
return stack.pop();
}
}