How to quickly and conveniently create a one element arraylist [duplicate]

Question

Is there a Utility method somewhere that can do this in 1 line? I can't find it anywhere in Collections, or List.

public List<String> stringToOneElementList(String s) {     List<String> list = new ArrayList<String>();     list.add(s);     return list; } 

I don't want to re-invent the wheel unless I plan on putting fancy rims on it.

Well... the type can be T, and not String. but you get the point. (with all the null checking, safety checks...etc)

Answer 1

Fixed size List

The easiest way, that I know of, is to create a fixed-size single element List with Arrays.asList(T...) like

// Returns a List backed by a varargs T. return Arrays.asList(s); 

Variable size List

If it needs vary in size you can construct an ArrayList and the fixed-sizeList like

return new ArrayList<String>(Arrays.asList(s)); 

and (in Java 7+) you can use the diamond operator <> to make it

return new ArrayList<>(Arrays.asList(s)); 

Single Element List

Collections can return a list with a single element with list being immutable:

Collections.singletonList(s) 

The benefit here is IDEs code analysis doesn't warn about single element asList(..) calls.