Varargs are useful for any method that needs to deal with an indeterminate number of objects. One good example is String.format. The format string can accept any number of parameters, so you need a mechanism to pass in any number of objects.
String.format("This is an integer: %d", myInt);
String.format("This is an integer: %d and a string: %s", myInt, myString);
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Varargs are useful for any method that needs to deal with an indeterminate number of objects. One good example is String.format. The format string can accept any number of parameters, so you need a mechanism to pass in any number of objects.
String.format("This is an integer: %d", myInt);
String.format("This is an integer: %d and a string: %s", myInt, myString);
A good rule of thumb would be:
"Use varargs for any method (or constructor) that needs an array of T (whatever type T may be) as input".
That will make calls to these methods easier (no need to do new T[]{...}).
You could extend this rule to include methods with a List<T> argument, provided that this argument is for input only (ie, the list is not modified by the method).
Additionally, I would refrain from using f(Object... args) because its slips towards a programming way with unclear APIs.
In terms of examples, I have used it in DesignGridLayout, where I can add several JComponents in one call:
layout.row().grid(new JLabel("Label")).add(field1, field2, field3);
In the code above the add() method is defined as add(JComponent... components).
Finally, the implementation of such methods must take care of the fact that it may be called with an empty vararg! If you want to impose at least one argument, then you have to use an ugly trick such as:
void f(T arg1, T... args) {...}
I consider this trick ugly because the implementation of the method will be less straightforward than having just T... args in its arguments list.
Hopes this helps clarifying the point about varargs.
Between a java method taking an arraylist of strings and varargs of strings, which is code style is more accepted? I've been working as a web dev for 2 years and only recently saw my first varargs. Seems like a great way to save time since I won't need to make an arraylist, add in items, and then pass it? Why haven't I been taught this earlier or seen this way of writing much earlier in my career?