Difference in System. exit(0) , System.exit(-1), System.exit(1 ) in Java

Question

I'd like to know the difference between the following in Java

System.exit(0);
System.exit(-1);
System.exit(1);

When do I have to use the above code appropriately?

Answer 1

The parameter of exit should qualify if the execution of the program went good or bad. It's a sort of heredity from older programming languages where it's useful to know if something went wrong and what went wrong.

Exit code is

• 0 when execution went fine;
• 1, -1, whatever != 0 when some error occurred, you can use different values for different kind of errors.

If I'm correct exit codes used to be just positive numbers (I mean in UNIX) and according to range:

• 1-127 are user defined codes (so generated by calling exit(n))
• 128-255 are codes generated by termination due to different unix signals like SIGSEGV or SIGTERM

But I don't think you should care while coding on Java, it's just a bit of information. It's useful if you plan to make your programs interact with standard tools.

Answer 2

Zero => Everything Okay

Positive => Something I expected could potentially go wrong went wrong (bad command-line, can't find file, could not connect to server)

Negative => Something I didn't expect at all went wrong (system error - unanticipated exception - externally forced termination e.g. kill -9)

(values greater than 128 are actually negative, if you regard them as 8-bit signed binary, or twos complement)

There's a load of good standard exit-codes here

Answer 3

System.exit(system call) terminates the currently running Java virtual machine by initiating its shutdown sequence. The argument serves as a status code.

By convention, a nonzero status code indicates abnormal termination.

  System.exit(0) or EXIT_SUCCESS;  ---> Success
  System.exit(1) or EXIT_FAILURE;  ---> Exception
  System.exit(-1) or EXIT_ERROR;   ---> Error

Read More at Java

On Unix and Linux systems, 0 for successful executions and 1 or higher for failed executions.

Answer 4

A non-zero exit status code, usually indicates abnormal termination. if n != 0, its up to the programmer to apply a meaning to the various n's.

From https://docs.oracle.com/javase/7/docs/api/java/lang/System.html.

Answer 5

exit(0) generally used to indicate successful termination. exit(1) or exit(-1) or any other non-zero value indicates unsuccessful termination in general.

Answer 6

Here is the answer.

System.exit(0);// normal termination - Successful - zero
System.exit(-1);//Exit with some Error
System.exit(1);//one or any positive integer // exit with some Information message

Answer 7

A good gotcha is any error code > 255 will be converted to error code % 256. One should be specifically careful about this if they are using a custom error code > 255 and expecting the exact error code in the application logic. http://www.tldp.org/LDP/abs/html/exitcodes.html

Answer 8

System.exit(0) by convention, a zero status code indicates successful termination.

System.exit(1) -It means termination unsuccessful due to some error

Answer 9

the difference of the numbers put in system.exit() is explained in other answers. but the REAL DIFFERENCE is that System.exit() is a code that gets returned to the invoking process. If the program is being invoked by the Operating system then the return code will tell the OS that if system.exit() returned 0 than everything was ok but if not something went wrong, then there could be some handlers for that in the parent process

Answer 10

As others answer 0 meaning success, otherwise.

If you using bat file (window) System.exit(x) will effect.

Code java (myapp):

if (error < 2){
    help();
    System.exit(-1);    
}
else{
    doSomthing();
    System.exit(0);
}

}

bat file:

java -jar myapp.jar
if %errorlevel% neq 0 exit /b %errorlevel%
rem -- next command if myapp is success --

Answer 11

Look at the code below

public static void main(String[] args) {
    **String s=null;**
    try {
        System.out.println("Exit");
        System.exit(1);
        **s.length();**
    }catch(Exception e) {
        System.out.println("Exception");
    }finally {
        System.out.println("finally");
    }}

Here exit(0) : Generally used to indicate successful termination. exit(1) or exit(-1) or any other non-zero value – Generally indicates unsuccessful termination. No matter what you pass as an argument, the control flow always comes out and doesn't print anything next, either it may be catch block as s.length will throw exception here or finally

Answer 12

class calc{
public static void main(String args[])
{
    int a, b, c;
    char ch;
    do{

        Scanner s=new Scanner(System.in);

                System.out.print("1. Addition\n");
                System.out.print("2. Substraction\n");
                System.out.print("3. Multiplication\n");
                System.out.print("4. Division\n");
                System.out.print("5. Exit\n\n");

                System.out.print("Enter your choice : ");
                ch=s.next().charAt(0);
                    switch (ch)
                    {
                        case '1' :
                        Addition chose1=new Addition();
                        chose1.add();
                        break;

                        case '2' :
                        Substraction chose2=new Substraction();
                        chose2.sub();
                        break;

                        case '3' :
                        Multiplication chose3= new Multiplication();
                        chose3.multi();
                        break;

                        case '4' :
                        Division chose4=new Division();
                        chose4.divi();
                        break;

                        case '5' :
                        System.exit(0);
                        break;

                        default :
                        System.out.print("wrong choice!!!");
                        break;
                    }
        System.out.print("\n--------------------------\n");                     
    }while(ch !=5); 
}

}

In the above code when its System.exit(0); and when i press case 5 it exits properly but when i use System.exit(1); and press case 5 it exits with error and again when i try with case 15 it exits properly by this i got to know that, when ever we put any int inside argument it specifies that, it take the character from that position i.e if i put (4) that it means take 5th character from that string if its (3) then it means take 4th character from that inputed string