The return type of a method gives the developer clues on what its function is doing.
For example:
| Return Type |
Meaning |
|---|---|
| boolean |
There can be a valid/successful result (true) or an invalid/unsuccessful result (false). Returning true or false is a normal occurrence.
Often a method that returns a boolean will have a name prefixed with “is....” or “has...” much like a getter for a boolean bean property. eg. isValid( ) |
| integer, long, float |
The method does a calculation/lookup/comparison for which the result is a number. |
| Integer, Long, Float |
The method does a calculation/lookup/comparison for which the result is a number. The result of the method can also be null, which usually means “not set” or “invalid”. |
| String |
The method does a calculation/lookup/comparison for which the result is a single word or phrase. The result of the method can be null unless otherwise defined in the javadoc. |
Tip: Any event that is not normally expected to occur can be identified with a thrown exception, but avoid using an exception to indicate an invalid result that will occur regularly.The following code is incorrectly using a non-blank string to indicate an invalid situation.
/**
* Check if it is a 'valid' company name
*/
public static String checkCompanyName(String companyName)
{
if (!cs.isCompanyIn(companyName))
{
return "Invalid company name: " + companyName;
}
return "";
}
The checkCompanyName method uses its return value for two completely different purposes and neglects to explain important things:
If a non-blank String is returned, it contains an error message.
Will the method ever return a null String?
If an empty “” String is returned, it is a valid company name.
This method should be changed to not use an error message at all:
/**
* Checks a company name to see if it is one we will accept orders from.
* @param companyName A company name.
* @return true if the company name is known, false if not
*/
public static boolean isValidCompanyName(String companyName)
{
return companies.contains(companyName);
}
Much cleaner. Note the appropriate use of javadoc as well.
