Someone

public class Test
{
	public static String FindUniqueChars(String s1, String s2)
	{
		String uniqueChars = "";
		for(int i=0; i<s1.length(); i++)
			for(int j=0; j<s2.length(); j++)
				if(s1.charAt(i) == s2.charAt(j))
					if(uniqueChars.indexOf(s1.charAt(i)) == -1)
						uniqueChars += s1.charAt(i);
		return uniqueChars;
	}
	
	public static void main(String[]args)
	{
		System.out.println(FindUniqueChars("apples", "ap"));
	}
}