Termination of program using if else statement?

Question

trying to terminate program using negative numbers and if else statement . does anyone see whats wrong with this thanks.

import java.util.Scanner;

public class Assignment {
    public static void main(String args[]){
    int n;
    int i=0;

    System.out.print("Enter a Number:");
    Scanner scanner = new Scanner(System.in);
    n= scanner.nextInt();
    int backUp = n;
    if(n>0)

        n=n/10;
        i++;

        else if(backUp = -1)

        System.out.print("program terminated......");
            System.exit(0);



    System.out.println("Number of Digits in " +backUp +" is " +i);

    }
}

You should use brackets around the if and else blocks { and } — Matthias
– Matthias, Commented Oct 9, 2013 at 8:40
I wonder why you don't use IDE 'cause it seems your code couldn't be even compiled successfully. I see you asked what's wrong with it..so compiler would answer :) and then we could discuss the logic. — java_newbie
– java_newbie, Commented Oct 9, 2013 at 9:23

BobTheBuilder · Accepted Answer · 2013-10-09 08:39:33Z

6

First of all, = is for assigning values. Use == for comparing.

Also, you need to use {} after if and else statements if you want to run more than one line.

answered Oct 9, 2013 at 8:39

BobTheBuilder

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5 Comments

Anthony Grist Over a year ago

@javaBeginner It is. If you look at the if(n>0) part, only the very next line will be dependent on the if statement, the next line (i++) will always execute, then the else if will result in a syntax error because it's not immediately after an if statement.

BobTheBuilder Over a year ago

Without {} the else has no meaning. And I think System.exit(0) should be called when exiting. (-1)

SpringLearner Over a year ago

i mean to say that when user enters any value greater than 0 then it will be terminated

Anthony Grist Over a year ago

@javaBeginner The intention seems to be that the user entering -1 will result in the program terminating, but any other input wouldn't.

MadProgrammer Over a year ago

@javaBeginner While technically you may be correct, it is always good practice to wrap your if statements in {}, prevents silly mistakes like the one presented - IMHO

Suresh Atta · Accepted Answer · 2013-10-09 08:39:47Z

4

   else if(backUp =  -1)

Should be

   else if(backUp == -1)

= assignment operator , == is for comparing

And finally with missed {}

  if (n > 0) {
            n = n / 10;
            i++;
   } else if (backUp == -1) {
            System.out.print("program terminated......");
            System.exit(0);
   }else{
          // do something else. I have no idea. 
        }

answered Oct 9, 2013 at 8:39

Suresh Atta

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Comments

Tobb · Accepted Answer · 2013-10-09 08:41:55Z

2

You are missing { } for your if-statements. In if statements without the { }, only the line following the if-statement will be affected by the outcome of the if-test.

So:

if (condition)
    doSomething();
    doSomethingElse();

will execute doSomething() if condition == true and doSomethingElse() no matter if condition == true.

if (condition) {
    doSomething();
    doSomethingElse();
}

will execute both doSomething() and doSomethingElse(), if and only if condition == true.

answered Oct 9, 2013 at 8:41

Tobb

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Comments

Scott Pearson · Accepted Answer · 2013-10-09 08:42:24Z

1

You are using an assignment operator to evaluate a condition.

else if(backUp = -1)

should be

else if(backup == -1)

answered Oct 9, 2013 at 8:42

Scott Pearson

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Comments

Rajendra arora · Accepted Answer · 2013-10-09 08:43:39Z

1

remove else use if(backup==-1).

answered Oct 9, 2013 at 8:43

Rajendra arora

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3 Comments

Suresh Atta Over a year ago

There is a difference between if and if else.

Anthony Grist Over a year ago

@AnubhavSharma Then tell him what the proper syntax is, don't tell him to completely change the way his code will execute.

Rajendra arora Over a year ago

it should be like this...if(n>0) { n=n/10; i++; } else if(backUp == -1)

Alowaniak · Accepted Answer · 2013-10-09 08:45:37Z

1

First of all your indenting.

Secondly, if you want to execute multiple statements given a certain condition you'll need to put it in a code block like if(x) { /* do multiple things */ }.

Thirdly, your else if(backUp = -1) is invalid because you need a boolean expression inside a if, backUp = -1 is an assignment and thus does not evaluate to a boolean (you probably want backUp == -1).

And you probably want to loop the n = n/10; i++; part because now it will never count more than 1 digit.

answered Oct 9, 2013 at 8:45

Alowaniak

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