CODEWITHSUNDEEP
javastringlistobjectsize
rapidash
rapidash

Reputation: 63

Creating a Method for multiple object types in Java

I'm a fairly new to Java and to programming, so excuse me if this is a stupid question.

I want to create a method exceptionchecker that does this 

public void exceptionchecker(Object check){
    if(check.size() == 0 && some_other_stuff) throw new IllegalArgumentException();
}

The problem is that the object passed might be a list or a string. So depending on the case I need to either use .length or .size().

Is there any easy way to do this, or am I better off creating two seperate methods?

EDIT: If it's relevant, the list would be of type String as well.

Upvotes: 2

Views: 396

Answers (6)

ColinD
ColinD

Reputation: 110046

I'd recommend just using something like Guava and its Preconditions class to do this sort of thing. Using static imports, you'd do something like:

checkArgument(something.size() > 0 || someOtherStuff);

It's easy enough to just put whatever checks there. In other words, just use a method that takes a boolean argument and do the actual checks outside the method.

Upvotes: 0

Sanjay T. Sharma
Sanjay T. Sharma

Reputation: 23208

Instead of passing an Object, consider passing in a wrapper object over the relevant type (String, List, Map etc.); for e.g. ExceptionData which honors the contract of implementing the isEmpty method. This exception data would have subclasses which override the isEmpty method when required.

Sure, this might result in a few more classes being created plus a few objects created at runtime, but unless you are dealing with a million such entities, this seems to be a far cleaner/explicit approach.

If this level of verboseness is not acceptable, consider method overloading to do your bidding which results in cleaner client code plus no creation of extra objects.

Upvotes: 1

Garbage
Garbage

Reputation: 1520

You might want to first check if the Object is of the type your method can handle using instanceof operator.

Upvotes: 0

Nikolaus Gradwohl
Nikolaus Gradwohl

Reputation: 20124

You could use check.class() to tests if the object is a string or list and cast it, but the more elegant method would be implementing an exception checker for every type you need 

void exceptionChecker( String check )  {
...
}

void exceptionChecker( List check )  {
...
}

void exceptionChecker( Object check )  {
...
}

Upvotes: 1

Vance Maverick
Vance Maverick

Reputation: 822

Having two signatures works if you know the type of the object at compile-time. At run-time, you can use instanceof to determine the type.

if (check instanceof Foo) {
  Foo foo = (Foo) check;
  if (foo.bar() == something) { ... }
}

Upvotes: 0

corsiKa
corsiKa

Reputation: 82559

You could use instanceof to do some checks, and it is reliable, but it doesn't leave it self as open to extension, or clarity.

The reason for this is

  • If you're checking something other than a list or a String, you should know about it at compile time
  • As you add more checks, it's going to cause a giant check method that will get tough to maintain.

Using two methods is most appropriate.

public void exceptionCheck(String s) {
    if(s.length() == 0) throw new IllegalArgumentException();
}

public void exceptionCheck(List<?> l) {
    if(s.isEmpty()) throw new IllegalArgumentException();
}

Upvotes: 2

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