String s = "ff0345f400";
int[] value = new int[s.length()/2];
for( int i = 0, j = 0; i < s.length(); i++, j++ ) {
StringBuilder tmp = new StringBuilder();
tmp.append( s.charAt(i));
tmp.append( s.charAt(i + 1) );
value[j] = Integer.parseInt( new String(tmp), 16 );
i++;
}