write code to remove the duplicate characters in a string

public static void removeDuplicates(char[] str) {
if (str == null) return;
int len = str.length;
if (len < 2) return;

int tail = 1;

for (int i = 1; i < len; ++i) {
int j;
for (j = 0; j < tail; ++j) {
if (str[i] == str[j]) break;
}
if (j == tail) {
str[tail] = str[i];
++tail;
}
}
str[tail] = 0;
}