Template Method Pattern Hints

Create an abstract base class called BinaryOperator
It should implement the Operator interface
Copy th method from one of the existing binary operator class, e.g., Add::execute
Put the result calculation it its own step, e.g., calculate(BigDecimal lhs, BigDecimal rhs), as an abstract method
One at a time, change the implementation of the various binary operator classes
- Extend your new abstract base calss
- Remove their execute method
- Implement the calcualte method
- Remove the implementation of the Operator interface
- Check your tests

Example of BinaryOperator

public abstract class BinaryOperator implements Operator {
    @Override
    public void execute(RpnStack values) {
        BigDecimal rhs = values.pop();
        BigDecimal lhs = values.pop();
        
        BigDecimal result = calculate(lhs, rhs);
        
        values.push(result);
    }

    abstract BigDecimal calculate(BigDecimal lhs, BigDecimal rhs);
}

Example of Add

public class Add extends BinaryOperator {
    @Override
    BigDecimal calculate(BigDecimal lhs, BigDecimal rhs) {
        return lhs.add(rhs);
    }
}

Example of BinaryOperator

Example of Add

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