OperationManager.java

import java.math.*;

public class Operation {
  double[] operatorsValues;

  void setOperatorsValues(double[] values) { operatorsValues = values; }

  String[] getOperationNames() {
    return String[]{this.getFirstOperationName(), this.getSecondOperationName()}
  }

  String getFirstOperationName() {
    return "Unknown";
  }

  String getSecondOperationName() {
    return "Unknown";
  }

  String perform() {
    return "Ooops!"
  }
}

public class SumOperation extends Operation {
  String getFirstOperationName() {
    return "first op";
  }

  String getSecondOperationName() {
    return "second op";
  }

  double perform() {
    return this.operatorsValues[0] + this.operatorsValues[1];
  }
}
public class DivOperation {
  String getFirstOperationName() {
    return "div op 1";
  }

  String getSecondOperationName() {
    return "div op 2";
  }

  double perform() {
    return this.operatorsValues[0] + this.operatorsValues[1];
  }
}

public class OperationFactory {
  static Operation build(code) {}
}



public class OperationManager {

    private int operation;

    public OperationManager(int input) {
        this.operation = OperationFactory.build(input);
    }

    public String[] returnArrayOfOperatorsName () {
        return this.operation.getOperationNames()
    }


    public String doOperation(double[] operators, int decimalRounding) {

        double result = 0;
        String sentence;
        char operationSign = '1';

        result = this.operation.perform();

        BigDecimal firstOperatorFormatted = new BigDecimal(operators[0]).setScale(decimalRounding, RoundingMode.DOWN);

        BigDecimal secondOperatorFormatted = new BigDecimal(operators[1]).setScale(decimalRounding, RoundingMode.DOWN);

        BigDecimal resultFormatted = new BigDecimal(result).setScale(decimalRounding, RoundingMode.DOWN);

        sentence = (firstOperatorFormatted + " " + operationSign + " " + secondOperatorFormatted + " = " + resultFormatted);

        return sentence;
    }
}