State the data type and value of res after the following is executed: char ch = '9'; res = Character.isDigit(ch);

Data type: boolean Value: true

Character.isDigit() asks a yes-or-no question, so it returns boolean. The character '9' IS a digit, so the value is true. Note the subtlety worth mentioning: '9' in single quotes is the CHARACTER nine, whose ASCII code is 57, not the number 9. isDigit() correctly recognises it as a digit character. Group the Character methods by return type: the is... methods return boolean, the to... methods return char.