Java Data Type - 如何检查字符是数字，字母，空格，小写还是大写字符

public class Main {

  public static void main(String[] args) {

    char a[] = { 'a', 'b', '5', '?', 'A', ' ' };

    for (int i = 0; i < a.length; i++) {

      if (Character.isDigit(a[i]))
        System.out.println(a[i] + "is a digit ");
      if (Character.isLetter(a[i]))
        System.out.println(a[i] + "is a letter ");
      if (Character.isWhitespace(a[i]))
        System.out.println(a[i] + "is a White Space ");
      if (Character.isLowerCase(a[i]))
        System.out.println(a[i] + "is a lower case ");
      if (Character.isLowerCase(a[i]))
        System.out.println(a[i] + "is a upper case ");
    }

  }
}