Eclipse編譯成功，丟上來編譯失敗，求Java高手相助，

以下是錯誤訊息以及我的Code：

第 1 測資點(0%): CE () 
編譯錯誤

/code_2098277.java:18: error: cannot find symbol 			list.sort(null); 			    ^   symbol:   method sort()   location: variable list of type ArrayList 1 error

 import java.util.ArrayList; import java.util.Scanner;  public class a010 { 	public static void main(String[] args) { 		Scanner sc = new Scanner(System.in); 		while (sc.hasNext()) { 			int n = sc.nextInt(); 			ArrayList<Integer> list = new ArrayList<Integer>(); 			for (int i = 2; i <= n; i++) { 				if (n % i == 0) { 					list.add(i); 					n /= i; 				} 			} 			if (n != 1) 				list.add(n); 			list.sort(null); 			if (list.size() == 1) 				System.out.print(list.get(0)); 			else { 				System.out.print(list.get(0)); 				for (int i = 1; i < list.size(); i++) { 					if (list.get(i) == list.get(i -1)) { 						System.out.print("^"+list.get(i)); 					} else 						System.out.print("*"+list.get(i)); 				} 			} 			System.out.println(); 		} 		sc.close(); 	} }