Could someone tell me how to put an error message in to the following code? If the user enters a number that is not between 0 and 12, how do I output "Invalid entry".
The program at the moment works fine and if an invalid character is entered the user is allowed to try again.
int hours; do { System.out.print("Enter hours: "); hours = myscanner.nextInt(); } while (hours < 0 || hours > 12); I would use an "infinite" while loop and break out of it when the hours figure is valid. while(true) { ... } is idiomatic Java.
Scanner scanner = new Scanner(System.in); int hours; while (true) { System.out.print("Enter hours: "); hours = scanner.nextInt(); if (hours >= 0 && hours <= 12) { break; } System.err.println("Invalid entry (should be 0-12)"); } 
int hours; boolean valid; do { System.out.print("Enter hours: "); hours = myscanner.nextInt(); valid = (hours >= 0 && hours <= 12); if (!valid) System.out.println("Invalid entry"); } while (!valid); NOTE: I've added a variable, because otherwise, you'd have duplicate condition there NOTE2: I've also reverted the condition because I don't like if booleans are referring to negative condition(I prefer valid over invalid)
int hours; do { System.out.print("Enter hours: "); hours = myscanner.nextInt(); if (hours < 0 || hours > 12) System.out.println("Please insert a valid entry"); } while (hours < 0 || hours > 12); 
if(....) System.out.println("Error");?