1. Methods Additional Topics
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2. Topics Returning values Name overloading
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3. The Return Type The first required part of the method header
May be any type – void, primitive or object
Consider examples: public static void main(…){…} static double fixer(int i){…} private char myFunction(…){…} String massage(String y){…}
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4. Notes The visibility is optional
public, private and protected are possible visibilities
The keyword static may be included or not
Depends on needs of the method
The return type is required for all methods
Other than constructors, which must return the object constructed
They also must have the same name as the class
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5. The return statement Has two effects
Ends the function and returns to calling statement
Determines the value that needs to be returned
Form is: return expression;
Expression should match return type
A void method needs no return
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6. Call return sequence
Consider this very simple sequence: static int four(){ return 4; } … public static void main(…) { System.out.println(four());
The method is called
The 4 is identified as the return value
This is displayed in the message
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7. Name Overloading
In many languages such as C, Pascal, VB a function is defined by one thing only: the function name
C++ introduced function name overloading
It determines the function to use by examining the signature
Java does the same
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8. Method Signatures
A method is uniquely determined by two things: the name the parameter list
The contribution of the parameter list does not include the parameter names, only number, type and order
These are collectively called the signature
Two signatures within a class may not be the same
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9. Example
Consider: int square(int a){ return a*a; } float square(float a){ return a*a; }
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10. Notes There is no conflict between the two
The compiler can tell which is intended
Consider: int i, j; float f,g; … int j = square(i); double g = square(f);
The result type does not distinguish
Only name and parameter types
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11. Why?
Function name overloading means that we can use the right name for a method
Even if the name has already been used
Both square methods did the same thing
Just on different types of parameters
Since types are so important we do not have to have a different name for the integer version as the double version
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12. Finally Most of this has been a review of previous material
It needs to extra emphasis
Methods are the building blocks of programs
Each of which is a class
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