if and else statements not working as intended

Question

I am making a really simple program, mostly to learn the if/else statements. The program is made to figure out if you have chosen a correct date.

The program is intended to work as follows:

Start the program, it gives you an instruction to type in a month using numbers.
If you type in a number between 1 and 12, it will give you another, similar instruction, but for days.
If you have chosen another number, or a word, it should say "month wrong". Depending on which month you have chosen, you will have different numbers of days that are "correct". If you have chosen right, it should say "Date correct".
If you have chosen a date that is not correct, it should say "Wrong day for the chosen month".

The problem is, that if you type for example 15 in the month section, it states

MonthWrongWrongdayinthemonthWrongdayinthemonth

instead of just

month wrong

Is this because I have if/else statements inside of other if/else statements? I have tried searching for this everywhere but I can not figure out what's wrong..

This is a link to a picture of the console when I try to run the app.

Picture of console

Please excuse the Swedish words.

import java.util.Scanner;

public class DateChecker111 {

    public static void main (String args[]) {

        Scanner scanner1 = new Scanner(System.in);

        int Manad, Dag;
        System.out.print("Ange Månad>");

        Manad = scanner1.nextInt();
        if (Manad > 0 && Manad < 13) {
        }
        else {
            System.out.print("Felaktig Månad");
        }

        if (Manad == 1 || Manad == 3 || Manad == 5 || Manad == 7 || Manad == 8 || Manad == 10 || Manad == 12) {
            System.out.print("Ange Dag>");
            Dag = scanner1.nextInt();
            if (Dag > 0 && Dag < 32); 
            System.out.print("Korrekt Datum");
        }
        else {
                System.out.print("Felaktig Dag i Månaden");
        }

        if (Manad == 2) {
            System.out.print("Ange Dag");
            Dag = scanner1.nextInt();
            if (Dag > 0 && Dag < 29); 
            System.out.print("Korrekt Datum");
        }
        else {
            System.out.print("Felaktig Dag i Månaden");
        }

        if (Manad == 4 || Manad == 6 || Manad == 9 || Manad == 11) {
            System.out.println("Ange Dag");
            Dag = scanner1.nextInt();
            if (Dag > 0 && Dag < 31);
            System.out.print("Korrekt Datum");
        } 
        else {
            System.out.print("Felaktig Dag i Månaden");

            scanner1.close();

        }
    }


}

[This seems to be fairly prevalent](http://stackoverflow.com/questions/14112515/semicolon-at-end-of-if-statement) in your code. — Obicere, Sep 17 '15 at 18:28

score 2 · Answer 1 · answered Sep 17 '15 at 18:46

The real problem here, and the root of all your troubles, is that you consistently end if statements with semicolons. For example, you write:

if (Dag > 0 && Dag < 32); 
    System.out.print("Korrekt Datum");

This is equivalent to having no if statement at all!

An if statement has the following form:

if (condition)
    statement

and an if-else statement has the following form:

if (condition)
    statement
else
    anotherStatement

Notice that I left off the semicolons and braces. That was deliberate. In either of those forms, statement and anotherStatement can either be a single statement ending in a semicolon, or a Block consisting of some number of statements inside braces. So when you end your if statement with a semicolon, you're actually writing

if (condition)
    ;

In the example code I quoted above, you're writing

if (Dag > 0 && Dag < 32)
    ; 
System.out.print("Korrekt Datum");

Take out the extra semicolons and your life will be happier.

score 1 · Answer 2 · answered Sep 17 '15 at 18:29

1

The execution flow of the appellation doesn't stop because a branch of the if/else has been executed, it will go on to execute the second if/else the result of which will also be output.

answered Sep 17 '15 at 18:29

Gavin

1,725
21
34

score 1 · Answer 3 · answered Sep 17 '15 at 18:35

Your second if-statement gets executed regardless whether the first one succeeds or not. To fix that, you can add

    return;

right after

    System.out.println("Felaktig Manad");

Also, be very careful with semicolons (;). There are multiple cases where you use a semicolon right after an if-statement which causes the if-statement to do nothing at all (it essentially gets skipped completely). Replace those semicolons with closing curly brackets (}). Depending on your IDE you can probably hit crtl+I so it indents your code automatically and you can see clearly what it does.

score 1 · Accepted Answer · answered Sep 17 '15 at 18:41

Below is your code formatted better so you can see the mistakes you've made. There are 3 if statements that end in ;, instead of a { as you intended. With the code formatted as it is now, you should notice that instead of a bunch of nested if statements, you have several if statements that will all be run, even if the first one fails. This is what you are seeing. To fix this, remove the ; at the end of the if statements, and add {. (I marked the bad ifs with // BAD IF)

import java.util.Scanner;

public class DateChecker111 {

    public static void main (String args[]) {

        Scanner scanner1 = new Scanner(System.in);

        int Manad, Dag;
        System.out.print("Ange Månad>");

        Manad = scanner1.nextInt();
        if (Manad > 0 && Manad < 13) {
        }
        else {
            System.out.print("Felaktig Månad");
        }

        if (Manad == 1 || Manad == 3 || Manad == 5 || Manad == 7 || Manad == 8 || Manad == 10 || Manad == 12) {
            System.out.print("Ange Dag>");
            Dag = scanner1.nextInt();

            // BAD IF
            if (Dag > 0 && Dag < 32);

            System.out.print("Korrekt Datum");
        } else {
            System.out.print("Felaktig Dag i Månaden");
        }

        if (Manad == 2) {
            System.out.print("Ange Dag");
            Dag = scanner1.nextInt();

            // BAD IF
            if (Dag > 0 && Dag < 29);

            System.out.print("Korrekt Datum");
        } else {
            System.out.print("Felaktig Dag i Månaden");
        }

        if (Manad == 4 || Manad == 6 || Manad == 9 || Manad == 11) {
            System.out.println("Ange Dag");
            Dag = scanner1.nextInt();

            // BAD IF
            if (Dag > 0 && Dag < 31);

            System.out.print("Korrekt Datum");
        } else {
            System.out.print("Felaktig Dag i Månaden");

            scanner1.close();

        }
    }
}

Thanks, that did indeed fix the original problem! But now, I have another one... The part that starts with if (Manad == 1 || .....) works, meaning that if I enter any of the numbers in that part, the application runs as it should. But, if I enter 2, 4, 6, 9 or 11, it terminates immidiately. I guess that this is because it only checks with the first "Manad" and not with the second and third... Any tips on this aswell? @forgivenson — Willee005, Sep 17 '15 at 18:51
Check the nesting of your if statements again. Your `if(Manad == 2)` is inside your `if(Manad == 1 || ....)`, which doesn't allow `Manad == 2`, so that if statement will never be reached. There could be other issues too. Make sure your code is indented properly, so you can see issues like this more easily. — forgivenson, Sep 17 '15 at 19:00
I figured it out! Used an else if statement on (Manad == 2) and (Manad == 4 ...) Thank you so much for your help! — Willee005, Sep 17 '15 at 19:13

score 0 · Answer 5 · answered Sep 17 '15 at 18:32

You have issues with your braces, see this code: if

(Manad == 1 || Manad == 3 || Manad == 5 || Manad == 7 || Manad == 8 || Manad == 10 || Manad == 12) {
        System.out.print("Ange Dag>");
        Dag = scanner1.nextInt();
        if (Dag > 0 && Dag < 32); 
            System.out.print("Korrekt Datum");
            }
            else {
                System.out.print("Felaktig Dag i Månaden");
        }

Your first closing brace } actually closes the main if. The code could be seen as:

if (Manad == 1 || Manad == 3 || Manad == 5 || Manad == 7 || Manad == 8 || Manad == 10 || Manad == 12) {
    System.out.print("Ange Dag>");
    Dag = scanner1.nextInt();
    if (Dag > 0 && Dag < 32); 
        System.out.print("Korrekt Datum");   
}
else {
    System.out.print("Felaktig Dag i Månaden");
}

score 0 · Answer 6 · answered Sep 17 '15 at 18:34

0

Replace the semicolon with bracket in this line:

if (Dag > 0 && Dag < 32);

answered Sep 17 '15 at 18:34

shiladitya

2,290
1
23
36

score 0 · Answer 7 · answered Sep 17 '15 at 18:40

You're Gavin said, the execution doesn't stop just because you enter a else statement, it keeps going from that point. If you want it to work as you expect it to you either have to put the code that should run only if the if-statement is true inside the if-block or introduce a return statement.

if(foo == 1) {
  if(bar == 2 {
    //Do something
  }
  else {
    //bar is not 2
  }
}
else {
  //foo is not 1
}

or

if(foo == 1) {
}
else {
  //foo is not 1
  return;
}
if(bar == 2 {
  //Do something
}
else {
  //bar is not 2
  return;
}

fullmoon · Answer 8 · 2015-09-17T19:03:49.530

You need to put your if(Manad == 2) inside the the else statement that belongs to if(Manad == 1..... Also put the if (Manad == 4.... inside the else statement of (Manad ==2). I did some comments and removed some brackets.

    Scanner scanner1 = new Scanner(System.in);

int Manad, Dag;
System.out.print("Ange Månad>");

Manad = scanner1.nextInt();
if (Manad > 0 && Manad < 13) {

    // you're not doing something here
}
else { 
    System.out.print("Felaktig Månad");
}

if (Manad == 1 || Manad == 3 || Manad == 5 || Manad == 7 || Manad == 8 || Manad == 10 || Manad == 12) {
    System.out.print("Ange Dag>");
    Dag = scanner1.nextInt();
    if (Dag > 0 && Dag < 32) {
        System.out.print("Korrekt Datum");
    }
}
else { // called if Manad != 1,3,5,7,8,10, or 12
    System.out.print("Felaktig Dag i Månaden");
}

if (Manad == 2) { // you may wanna put this if else statement inside the previous else
    System.out.print("Ange Dag");
    Dag = scanner1.nextInt();
    if (Dag > 0 && Dag < 29) {
        System.out.print("Korrekt Datum");
    }
}
else { // for now, this is called every time Mannad != 2 
    System.out.print("Felaktig Dag i Månaden");
}

if (Manad == 4 || Manad == 6 || Manad == 9 || Manad == 11) { 
    // put this if else statement inside else that belongs to Manad == 2
    System.out.println("Ange Dag");
    Dag = scanner1.nextInt();
    if (Dag > 0 && Dag < 31) {
        System.out.print("Korrekt Datum");
    }
}
else {// for now, this is called every time Manad != 4,6,9, or 11
    System.out.print("Felaktig Dag i Månaden");

    scanner1.close();

}

@forgivenson said the opposite a bit down "Check the nesting of your if statements again. Your if(Manad == 2) is inside your if(Manad == 1 || ....), which doesn't allow Manad == 2, so that if statement will never be reached." So which one is it, is it nested in and needs to be taken out or vice versa? — Willee005, Sep 17 '15 at 19:06
if Manad doesn't satisfy if(Manad ==1 || ...) then the else after it is called so if you put if(Manad == 2) statement inside that else it will always be checked as long as Manad != 1,3,5.... — fullmoon, Sep 17 '15 at 19:13
same thing with if(Manad ==4 ||....) if you put it inside the else statement that belongs to if(Manad == 2), it will be always reached as long as if(Manad ==1 || ...) and if(Manad == 2) were not satisfied. — fullmoon, Sep 17 '15 at 19:18

if and else statements not working as intended

8 Answers8