1. Chapter 10 Making Method Calls Simpler ¶

The name of a method does not reveal its purpose.

A method needs more information from its caller.

A parameter is no longer used by the method body.

You have a method that returns a value but also changes the state of an object.

Several methods do similar things but with different values contained in the method body.

You have a method that runs different code depending on the values of an enumerated parameter.

~cpp 
void setValue (String name, int value) {
	if (name.equals("height"))
		_height = value;
	if (name.equals("width"))
		_width = value;
	Assert.shouldNeverReachHere();
}

~cpp 
void setHeight (int arg) {
	_height = arg;
}
void setWidth (int arg) {
	_width = arg;
}

You are getting several values from an object and passing these values as parameters in a method call.

~cpp 
int low = daysTempRange().getLow();
int high = days.TempRange().getHight();
withinPlan = plan.withinRange (low, high);

~cpp 
withinPlan = plan.withinRange (daysTempRange());

An object invokes a method, then passes the result as a parameter for a method. The receiver can also invoke this method.

~cpp 
int basePrice = _quantity * _itemPrice;
discountLevel = getDiscountLevel ();
double finalPrice = discountedPrice (basePrice, discountLevel);

~cpp 
int basePrice = _quantity * _itemPrice;
double finalPrice = discountedPrice (basePrice);

You have a group of parameters that naturally go together.

A field should be set at creation time and never altered.

A method is not used by any other class.

You want to do more that simple construction when you create an object.

~cpp 
Emplyee (int type) {
	_type = type;
}

~cpp 
static Emplyee create (int type) {
	return new Emplyee (type);
}

A method returns an object that needs to be downcasted by its callers.

~cpp 
Object lastReading () {
	return readings.lastElement ();
}

~cpp 
Reading lastReading () {
	return (Reading) readings.lastElement ();
}

A method returns a special code to indicate an error.

~cpp 
int withdraw(int amount) {
	if (amount > _balance)
		return -1;
	else {
		_balance -= amount;
		return 0;
	}
}

~cpp 
void withdraw(int amount) throws BalanceException {
	if (amount > _balance) throw new BalanceException ();
	_balance -= amount;
}

You are throwing an exception on a condition the caller could have checked first.

~cpp 
double getValueForPeriod (int periodNumber) {
	try {
		return _values[periodNumber];
	} catch (ArrayIndexOutOfBoundsException e) {
		return 0;
	}
}

~cpp 
double getValueForPeriod (int periodNumber) {
	if (periodNumber >= _values.length) return 0;
	return _values[periodNumber];
}