Expression can be simplified. Checkstyle

Question

How can I simplify this? The variable fuel is a boolean from a parent class named Vehicle. The useTax() method is an abstract method from the same Vehicle class.

When I go about running checkstyle, it comes up with the string "Expression can be simplified." and highlights if (fuel == true).

public double useTax() {
    double tax;
    if (fuel == true) { // <-- why?
        tax = value * ALTERNATIVE_FUEL_TAX_RATE;
    }
    else {
        tax = value * TAX_RATE;
    }
    if (value > LUXURY_THRESHOLD) {
        tax += value * LUXURY_TAX_RATE;
    }
    return tax;
}

Answer 1

I think it's telling you that

if (fuel == true)

can be written more concisely as

if (fuel)

Answer 2

I think what it means is instead of "if(fuel == true)", you can simplify it too "if(fuel)"

Answer 3

if (fuel == true)

Here your code has unnecessary boolean redundancy.

You can just use

if (fuel)