CharBuffer { static boolean isDigit(char c) { return c >= '0' && c <= '9'; } private  CharBuffer(char[] cs); @Override String toString(); public char[] cs; public int position; }
@Test public void isDigit() { for (char c = '0'; c <= '9'; c++) assertTrue(CharBuffer.isDigit(c)); for (char c = 'a'; c <= 'z'; c++) assertFalse(CharBuffer.isDigit(c)); for (char c = 'A'; c <= 'Z'; c++) assertFalse(CharBuffer.isDigit(c)); }