Java, I am having trouble executing this source code. please help

// The class LongestStringMain is used to determine the longest string in the array

// In the main() function, create the object

// In the compare() method

// Determine the length of two strigs and subtract one string from another string

// and return the result.

// Initialize the array list element values

// Call the maximum() method to determine the longest string in the array list.

// Display the longest string in the array list.

// In the maximum() method

// Declare and initialize the variable.

// The for loop compares the two string to find the longest string in the array list.

// if yes, call the compare() method to determine the longest string and

// check whether the longest string is greater thann 0.

// if yes, asssign test tring into "max" variable

// Return the longest string

/* This program demonstrates to find the longest string in the array list */

import java.util.ArrayList;

import java.util.Comparator;

// The class LongestStringMain is used to determine the longest string in the array

public class LongestStringMain{

// The main() function creates a object for ArrayList class and Comparator interface,

// initializes the values for that array element, and determines the longest string

// in the array list by calling maximum() method.

@SuppressWarnings({ "rawtypes", "unchecked" })

public static void main(String[] args){

// create an object "aObj" for ArrayList class

ArrayList aObj = new ArrayList();

// create an object "cObj" for Comparator interface

Comparator cObj = new Comparator(){

// the compare() method accepts "s1" and "s2" as input parameter to determine

// the length of two string and subtract one string from another string and return the result

@SuppressWarnings("unused")

public int compare(String s1, String s2){

// subtract the string from another string and return the result

return s1.length() - s2.length();

}

@Override

public int compare(Object o1, Object o2) {

// TODO Auto-generated method stub

return 0;

}

};

// initialize the array list element values

// assign the string into array list element

aObj.add("kkkk");

aObj.add("aa");

aObj.add("bbbbbb");

aObj.add("ccc");

// call the maximum() method to determine the longest string in the array list

// call the method to find the longest strig in the array element

String max = maximum(aObj, cObj);

// display the longest string in the array element

System.out.printf("The longest string is : " + max);

}

// the maximum() method accepts "a" and "c" as inpout parameters to determine

// the longest string in the array list. method definition

@SuppressWarnings({ "rawtypes", "unchecked" })

public static String maximum(ArrayList a, Comparator c){

// declare the string variable and get the array values as "0"

String max = (String) a.get(0);

// the for loop compares the two string to find the longest string in the array list

// loop compare the string "test" from "a"

for(String test:a){

// call the compare() method to determine the longest strig and check whether

// the longest string is greater than 0. if yes, assign test string into "max" variable

// verify the longest string greater than 0

if(c.compare(test, max) > 0)

// assign test into "max" variable

max = test;

}

//return the longest string in the array

return max;

}

}