Question

I have list of String.
List<String> elements= new ArrayList<String>();
when I wanna add new String

elements.add(“element”);

with name which is my arraylist I wanna to automatically rename to _[a-z…] as windows rename file when there are two same… so for example I have in arraylist “element” when I add element again I wanna to rename automatically to element_a … so

    if (elements.contains("element")) { 
    something
}

is there some function in java ?
thx for help

Answer 1

No built-in function, but it’s not too hard. For example:

public static void main(String[] args) {
    List<String> l = new ArrayList<String>();
    add("foo", l);
    add("foo", l);
    add("foo", l);
    add("foo", l);
    add("foo", l);
    add("foo", l);
    add("foo", l);
    add("foo", l);
    System.out.println(l);
}

static void add(String element, List<String> elements) {
    if (elements.contains(element)) {
        elements.add(nextValudFor(element, elements));
    } else {
        elements.add(element);
    }
}

static String nextValudFor(String element, List<String> elements) {
    for (char c = 'a'; c <= 'z'; c++) {
        String next = element + '_' + c;
        if (!elements.contains(next)) {
            return next;
        }
    }
    throw new IllegalStateException("Ran out of letters!");
}

Outputs:

[foo, foo_a, foo_b, foo_c, foo_d, foo_e, foo_f, foo_g]

For best effect, you’d probably want to wrap this up into your own List type as appropriate.