Euler4.java

import static java.lang.System.out;

import java.util.ArrayList;
import java.util.List;

public class Euler4
{
	static final int MIN = 100;
	static final int MAX = 999;	
	
	public static List<Integer> getPalindromes(int min, int max)
	{
		List<Integer> palindromes = new ArrayList<>();
		for (int i=max; i >= min; i--)
		{
			for (int j=max; j >= min; j--)
			{
				int product = i * j;
				if (isPalindrome(new Integer(product).toString()))
					palindromes.add(product);
			}
		}		
		return palindromes;
	}
	
	public static boolean isPalindrome(String str)
	{
		if (str.length() < 0) return false;
		if (str.length() <= 1) return true;
	
		char firstChar = str.charAt(0);
		char lastChar = str.charAt(str.length()-1);
		
		if (firstChar == lastChar) {
			return isPalindrome(str.substring(1, str.length()-1));
		}
		return false;
	}
	
	public static int getHighestNumber(List<Integer> numbers)
	{
		int highestNumber = -1;
		for (int number : numbers)
			if (number > highestNumber)
				highestNumber = number;
		return highestNumber;
	}
	
	public static void main(String[] args)
	{
		List<Integer> palindromes = getPalindromes(MIN, MAX);
		out.println(getHighestNumber(palindromes));
	}
}