Defining Classes I - Java - page 215

PITFALL: You Cannot Overload Based on the Type Returned

If you think about it, there is no way that Java could allow this sort of overloading.
Suppose anObject is an object of the class SampleClass2 . Then in the following
assignment, Java could not decide which of the above two method definitions to use:

double answer = anObject.computeSomething(10);

Either a value of type int or a value of type double can legally be assigned to the vari-
able answer . So, either method definition could be used. Because of such problems,
Java says it is illegal to have both of these method headings in the same class.

■

You Cannot Overload Operators in Java
Many programming languages, such as C++, allow you to overload operators, such as + , so
that the operator can be used with objects of some class you define, as well as being used
for such things as numbers. You cannot do this in Java. If you want to have an “addition” in
your class, you must use a method name, such as add , and ordinary method syntax; you
cannot define operators, such as the + operator, to work with objects of a class you define.

Self-Test Exercises
20. What is the signature of each of the following method headings?

public void doSomething( int p1, char p2, int p3)
public void setMonth( int newMonth)
public void setMonth(String newMonth)
public int amount( int balance, double duration)
public double amount( int balance, double duration)

21. Consider the class DateSixthTry in Display 4.11. Would it be legal to add two
method definitions with the following two method headings to the class
DateSixthTry ?

public void setMonth( int newMonth)
public void setMonth(String newMonth)

22. Consider the class DateSixthTry in Display 4.11. Would it be legal to add two
method definitions with the following two method headings to the class
DateSixthTry ?

public void setMonth( int newMonth)
private void setMonth( int newMonth)