Check no duplicates in a char array

E.g.row = 5 col = 4. To check if the 5th bit is ‘1’. Set the other bits to zero.

int mask = 1 << col;

if (set[row] & mask != 0) return true;

Else set the 5th bit to ‘1’. set[row] = set[row] |  mask;

bits[4]    0000 0000 0000 0000 0000 0000 0000 0000

mask     0000 0000 0000 0000 0000 0000 0001 0000

public boolean checkUnique(char[] array) {

if (array == null) return true; //Or throw IllegalArgumentException

int[] set = new int[8]; //All together 8 * 32 positions

for (char c : array) {

int row = c / 32;  //integer access

int col = c % 32; //bit access

int mask = 1 << col;

if (set[row] & mask != 0) return false;

set[row] = set[row] | mask;

}

return true;

}

public boolean checkUnique(char[] array) {

try {

if (array == null) throw new IllegalArgumentException();

int[] set = new int[8]; //All together 8 * 32 positions

for (char c : array) {

int row = c / 32;  //integer access

int col = c % 32; //bit access

int mask = 1 << col;

if (set[row] & mask != 0) return false;

set[row] = set[row] | mask;

}

return true;

} catch (IllegalArgumentException e) {

System.out.println(“Input array is null.”);

}

}