Question

I have a class with as private List<String> children; which is currently initialized in the constructor but this is not always needed and I want to initialize it only when some other function need it.

The whole point is to rework current implementation without changing to much code.

I know how to do it in other languages, but Java knowledge is quite limited, so far.

Answer 1

To spell it out, this is one way of accomplishing it:

public class Whatever 
{
    private List<String> children;

    public List<String> getChildren
    {
        if ( children == null ) { children = new ArrayList<String>(); }
        return children;
    }
    ...
}

Also, remember to write eg. addChild( String child ) in terms of the get‘er rather than directly accessing the field. And if you’re really paranoid and/or in a threaded environment and the creation takes a long time, you might want to make the block synchronized.