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Static Methods

Adam Favel

Joined: Feb 09, 2005
Posts: 22
does Java allow someone to return more than one answer or number when using the "return" function in a static method.

for example:

if (a>b && b>c)

a >b

return a;
return b;

can you actually do this?

Paul Sturrock

Joined: Apr 14, 2004
Posts: 10336

If you mean "can I return one thing or another from a method?" like this:

then the answer is yes.

If you mean "Can I return two things from a method?" then the answer is also yes:

If you mean "can I call return twice to return two things?" then the answer is no. The reason is shown in the first example - return will 'exit' the method.
[ March 08, 2005: Message edited by: Paul Sturrock ]

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Joel McNary

Joined: Aug 20, 2001
Posts: 1824

Another trick to use (and, yes people, feel free to tell me that this isn't a good design... ) is output parameters. In C, this is typically doen with pointers-to-pointers, but in Java, we don't have pointers. But we do have arrays.

As I say, this is generally not good programming practice. Usually, I use this as is only a temporary approach, and wind up refactoring the method call into two methods or returning a complex type down the road.

Piscis Babelis est parvus, flavus, et hiridicus, et est probabiliter insolitissima raritas in toto mundo.
James Carman
Ranch Hand

Joined: Feb 20, 2001
Posts: 580
Yes, using array types to store individual return values which must be picked off from the correct indices isn't good practice (unless it's an obvious one like coordinates or something). As Joel said, it's better to define a "complex" type that holds your values and exposes them in a more meaningful manner. Then, your API tells you what it's doing rather than requiring someone to read your documentation to figure out which index to use to get what value. Also, if you do ever need to add stuff to the return value, it's much easier, especially if you were to want to add something into the middle of the array.

James Carman, President<br />Carman Consulting, Inc.
Russ Ray
Ranch Hand

Joined: Feb 11, 2003
Posts: 52

Look at the interface called Serializable. Here is how I would use it.

Class A implements Serializable

Class B implements Serializable

Class C implements Serializable

public Serializable doSomething(Object E)
if (E instanceof A)
return (A)E;
else if(E instanceof B)
return (B)E;


Also you can do this using the Object class. The only stipulation I would say is that you must use the "instanceof" facility.

Best of luck,

Ilja Preuss

Joined: Jul 11, 2001
Posts: 14112
Russ, using Serializable doesn't buy you anything in your example, you could simply use Object as return type.

Type cases (your if statements using instanceof) are a bad idea, though - they fly in the face of OO programming. It's much better to use polymorphic behaviour instead.

The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus
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