首个重复字符

import java.util.*;

public class FirstRepeat {
         public char findFirstRepeat(String A, int n) {

        if (A==null||A.length()<=0) {
            return 0;
        }
        char[] ch = A.toCharArray();
        return find(ch);
    }

    private char find(char[] array) {
        int[] a=new int[255];
        for (int i = 0; i < array.length; i++) {
            if (a[array[i]]==0){
                a[array[i]]++;
            }else return array[i];
        }
        return 0;
    }
}