Question

I have an ArrayList of type String. I want to determine whether any element of this ArrayList starts with a specified string and if the ArrayList contains this element, then I want to get the index of this element. In addition, I do not want to loop this ArrayList to get the index of that element.

For example :

ArrayList<String> asd = new ArrayList<String>();  // We have an array list

//We filled the array list
asd.add("abcc trtiou");
asd.add("aiwr hiut qwe");
asd.add("vkl: gtr");
asd.add("aAgiur gfjhg ewru");

Now, I want to get the index of the element vkl: gtr by using vkl: without looping array list.(searching also should be case insensitive, so, using vkl: and VkL: should give the index of vkl: gtr)

How can I do this ?

Thanks in advance.

Answer 1

You have to loop the ArrayList. You cant possibly access just a single index and be guaranteed it is what you’re looking for.

Also, you should consider using another data structure if a lot of searching is involved. Searching an ArrayList takes O(n)time while something like a red-black tree can be done in O(log n).

If you know before program execution the strings used to locate the items in the structure, consider using a HashMap. You can access the items in O(1).

If none of these solutions suit your particular problem expand on your answer with what you’re trying to do, we could provide a better answer as to how you’d locate your items with minimal search time.