Thread: Java while loops and switches

Hi,
I'm a beginner at Java programming and I was wondering if anyone could help / explain how to use a while loop in a task. The task is to create a menu which is appears constantly after the user has made an input. The user should enter instructions in the form of the numbers 1 to 4 as follows:
1 - Reroll the dice
2-get the value
3-show maximum
4-show minimum
Once the user has entered a number and an instruction is made the menu must re-appear asking the user to make a choice again. This must happen repeatedly
Example:
User enters: 4
Program displays: "The minimum value is: n"
Then the menu reappears asking the user to make another choice
I understand I need to use a while loop (and maybe a switch) but I’m unsure how to make this happen.
I'm not really good at explaining things so I apologize if anything is unclear or just confusing.

//Asks the user to input a number for dices sides
System.out.println("How many sides should the dice have?") ;
int numberOfSides ;
Scanner scanner = new Scanner (System.in);
numberOfSides = scanner.nextInt() ;
Dice2 d= new Dice2 (numberOfSides);
 
// The user can only enter 4,6,8,12,20 or 100
//Any other number should terminate the program
if ( numberOfSides == 4 || numberOfSides == 6 || numberOfSides == 8 || numberOfSides == 12 ||numberOfSides == 20 ||numberOfSides == 100 ){
[B]once the number of sides is declared this menu should appear [/B]
System.out.println("Please make a choice:") ;
System.out.println("1 - reroll the dice") ;
System.out.println("2 - get the value") ;
System.out.println("3 - show the maximum") ;
System.out.println("4 - show the minimum") ;
} else {
System.exit(0);
} // closing else statement
 
//Storing the users choice and current value of the dice
int choice ;
choice = scanner.nextInt() ;
int currentValue;
currentValue = d.getValue() ;
 
[B]This is suppose to be a while loop which makes the menu re-appear after the user has made a choice[/B]
while (choice == 1 || choice == 2 || choice == 3 || choice == 4) {
System.out.println("Please make a choice:") ;
System.out.println("1 - reroll the dice") ;
System.out.println("2 - get the value") ;
System.out.println("3 - show the maximum") ;
System.out.println("4 - show the minimum") ;
choice++;
 
//after the user enters a choice either one of the cases become true... any other number should terminate the program
switch (choice) {
case 1: d.reroll();
break;
case 2: System.out.println("The current value is " + currentValue);
break;
case 3: int maximum = Math.max(currentValue, numberOfSides);
break;
case 4: int minimum = Math.min(currentValue, numberOfSides);
System.out.println("The minimum is " + minimum) ;
break;

I did make a loop using the if statement however after submitting the lectures feedback was not to use to many if statements

while (condition) {
statement;
}

Basically if the condition is true then the statements are executed until the condition becomes false.

Example:

int num = 5;
while (num <= 5) {
num++;
System.out.println("*");
}

5 is smaller than 5 4 times and equal to 5 once. This means the statement will be executed 5 times.

Scanner scan = new Scanner (System.in);
String example;
System.out.print("Enter a word: ");
example = scan.nextLine();
 
switch (example) {
 
case "no":
System.out.println("This is just an example.");
break;
 
case "yes":
System.out.println("This is just an example.");
break;
}

So basically it will execute the tasks of the case matched.

Edit: you can also use default while using the switch (basically means anything but the above cases).

Originally Posted by Norm

@D.K Did you test that code? How many times did the execute the statement in loop?



You should ALWAYs use the default to catch unexpected input.

Opps, forgot that was an infinite loop XD.

Edit: if you add num++; in the while loop that will fix the infinite loop (increments num by 1 each time).