CODEWITHSUNDEEP
javamethodsgetreturn-value
Alex
Alex

Reputation: 3181

Are getters for objects any different than ones for primitives?

Should getters just return the object:

public MyObject getMyObject() {
    return myObject;
}

Or should it make a copy of the object it's returning and return the copy?

public MyObject getMyObject() {
    MyObject tempObject;
    // call setters to set its attributes
    return tempObject;
}

High school "CS" courses here aren't detailed enough. My teacher never talked about classes, objects, and references.

Upvotes: 2

Views: 93

Answers (2)

ziesemer
ziesemer

Reputation: 28697

The only difference is that while returned primitives are "immutable" by nature, returning an object directly like this could allow the caller to change properties on it (assuming that MyObject is mutable), possibly affecting the internals of your class's implementation. (Code analysis tools like FindBugs check for exactly this. Primitives are actually mutable, but when returned from a class, there is no way to update the class's value through the returned primitive.) That considered, it's usually a safer bet to return a copy / clone - understanding there may be a performance penalty involved in doing this.

With whatever option you choose, please document what your class or individual methods do using Javadoc.

Upvotes: 3

tsm
tsm

Reputation: 3658

This depends on what you're trying to do.

In general, though, you just want a reference to the object, and you use your first code example. For example, Swing components have a method called getTopLevelAncestor(). It's completely useless to have a copy of the parent component--what's wanted is a reference to the child's actual parent.

Returning a copy is not standard, and should only be used under very specific (and well-documented) circumstances. Other people using your code will not expect to get copies of objects.

Upvotes: 4

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