How to add option to exit from switch case in Java

Question

I am creating a menu based program in java using switch case. here are 4 cases:

1. add record
2. delete record
3. update record
4. Exit

I added break after each case but, what I want to do is to terminate the program when user enter case no 4 so what to do in this case ?

Answer 1

Please don't use System.exit. It's like trying to use a chainsaw to slice a tomato. It's a blunt tool that might be useful for emergency situations, but not for normal situations like you're trying to write.

There are a couple better approaches: (1) If you put your loop in a method, where the method's only purpose is to read the user's input and perform the desired functions, you can return from that method:

private static void mainMenu() {
    while(true) {
        char option = getOptionFromUser();
        switch(option) {
            case '1':
                addRecord();
                break;
            case '2':
                deleteRecord();
                break;
            case '3':
                updateRecord();
                break;
            case '4':
                return;
        }
    }
}

Now, whatever program calls mainMenu() has an opportunity to do some cleanup, print a "goodbye" message, ask the user if they want to back up their files before exiting, etc. You can't do that with System.exit.

Another mechanism, besides return, is to use break to exit the loop. Since break also breaks out of a switch, you'll need a loop label:

private static void mainMenu() {
    menuLoop:
    while(true) {
        char option = getOptionFromUser();
        switch(option) {
            ... as above
            case '4':
                break menuLoop;
        }
    }
    ... will go here when user types '4', you can do other stuff if desired
}

Or (as Riddhesh Sanghvi suggested) you can put a condition in the while loop instead of breaking out of it. His answer used a condition based on the option; another idiom I've used a lot is to set up a boolean for the purpose:

private static void mainMenu() {
    boolean askForAnother = true;
    while(askForAnother) {
        char option = getOptionFromUser();
        switch(option) {
            ... as above
            case '4':
               askForAnother = false;
        }
    }
    ... will go here when user types '4', you can do other stuff if desired
}

Or:

private static void mainMenu() {
    boolean done = false;
    do {
        char option = getOptionFromUser();
        switch(option) {
            ... as above
            case '4':
                done = true;
        }
    } while (!done);
}

So you have a lot of options, all better than System.exit.

Answer 2

If you do not wish to choose either return or System.exit(ExitCode) then put the termination condition in while loop as shown below.
Why to put while(true) and then put return or System.exit instead exploit the boolean check of the while loop to exit it.

private static void mainMenu() {
    int option=0;//initializing it so that it enters the while loop for the 1st time 
    while(option!=4){
        option = getOptionFromUser();
        switch(option) {
            case 1:
                addRecord();
                break;
            case 2:
                deleteRecord();
                break;
            case 3:
                updateRecord();
                break;
            case 4:
                System.out.print("While Loop Terminated");
                break;
        }
    }
    // when user enters 4,
    //Will execute stuff(here the print statement) of case 4 & then
    //... will come here you can do other stuff if desired
}

Answer 3

You can use System.exit() for this purpose.

System.exit(int status)

Terminates the currently running Java Virtual Machine.

Answer 4

Whenever You want to Exit out of the Switch case it is always better to use a do-while loop because that gives the user an advantage of running the Program again if he wants to update, delete or add Multiple records as in your Program

class record{
public static void main(String args[]){
do
{
System.out.Println("Enter Choice ");
Scanner sc = new Scanner(System.in);
int choice = sc.nextInt();
switch(option){
case 1:{
//Code for Adding the Records
break; 
}
case 2:{
//Code for deleting the Records
break;
}
case 3:{
//Code for Updating the Records 
break;
}
case 4:{
break; 
      }
   }
}
while(choice!=4);
    }
}

Wherever you want to add the Code for adding,deleting and updating the records you can call the Methods also which are defined outside the Switch Case and the Program should run just fine

Answer 5

return OR System.exit(ExitCode) if you want to exit directly.

Answer 6

In case no 4, add:

System.exit(int status);

Usually, status >= 0 indicates that the program terminated correctly and status < 0 indicates an abnormal termination. I think you should use:

System.exit(0);

status serves as errorCode. You can assign whatever value you want. If your program contains many exit points, you can assign different errorCodes to them. You can return the errorCode to the environment which called the application. Through this errorCode, you can trace which System.exit() caused the program to terminate.

Answer 7

Your particular case in your switch statement would be:

case 4: System.exit(0);

Answer 8

float ans;

    switch(operator)
    {
        case '+':
            ans = no1 + no2;
            break;

        case '-':
            ans = no1 - no2;
            break;

        case '*':
              ans = no1 * no2;
            break;

        case '/':
              ans = no1 / no2;
            break;
    case '0':
    System.exit(0);

        default:
            System.out.printf("EERRRoOOOORRR(^!^)");
            return;
    }