Eclipse not recognizing StringBuilder?

Question

Eclipse isnt recognizing StringBuilder for some reason. This program just prompts for user and nothing afterwards. This code has no compilation errors. Does anyone know a reason this may be happening?

ex. of output:

Enter a string:

enter new string

import java.util.*;
public class StringBuilder001{

public static void main(String[] args) {
    // TODO Auto-generated method stub

    Scanner s = new Scanner(System.in);
    StringBuilder sb = new StringBuilder();

    System.out.println("Enter a string:\t");
    String input = s.nextLine();
    String[] arr = input.split(input);

    for (int i = arr.length-1; i>=0 ; i--)
        sb.append(arr[i]);

    System.out.println(sb);

Answer 1

The bug is in the

 String[] arr = input.split(input);

It should be ( or some other split char)

String[] arr = input.split(" ");