Can someone help me with this?

Can someone help me with this? 

code:

public class ArrayListFun {

/**
* Counts the number of instances of a particular value in list.
* Returns null if list is null.
*
* @param list
* @param checkNum
* @return the number of Integer occurrences in list equal to checkNum
*/
public static Integer countOccurrences(ArrayList<Integer> list, int checkNum) {
// TODO: FILL IN BODY
return null;
}

/**
* Calculates the sum, product, or mean of all values in list.
* Returns null if list is null.
*
* @param list
* @param operation
* @return the sum, product, or mean of all values in list
*/
public static Integer mathOperation(ArrayList<Integer> list, String operation) {
// TODO: FILL IN BODY
return null;
}

/**
* Converts the 1s and 0s in list (binary value) to its decimal value
*
* Example: 100110 from binary to decimal
*
* 1 * 2^5 +
* 0 * 2^4 +
* 0 * 2^3 +
* 1 * 2^2 +
* 1 * 2^1 +
* 0 * 2^0 =
* 38
*
* For more information on binary, see zyBooks chapter 3.1
*
* Returns null if list is null.
*
* @param list
* @return the decimal value of the binary representation of list
*/
public static Integer binaryToDecimal(ArrayList<Integer> list) {
// TODO: FILL IN BODY
return null;
}

/**
* Returns true if list is a (character) palindrome.
* Returns null if list is null.
*
* @param list
* @return true if the list is a palindrome, else false.
*/
public static Boolean isPalindrome(ArrayList<Character> list) {
// TODO: FILL IN BODY
return null;
}

public static void main(String[] args) {
// TODO: FILL IN BODY
}
}