Java Switch Statement

Question

I have a problem using switch statement when I tried to deal with a special situation. For example, I have 3 cases: A, B, C.

for A, I want to do statement_1 and statement_3.
for B, I want to do statement_2 and statement_3.
for C, I want to do nothing

if I use if-else statement, it will look like the following:

 if ( not C){
    do statement_3

   if B
      do statement 2
   else if A
      do statement 1

 }

If I want to use switch statement to do the same thing, I have some trouble.

switch (variable){
case A:  do statement_1
case B: do statement_2
// how to do statement 3 here?  
}

I am trying to avoid the duplicated codes. So I am thinking that how to make the codes as simple as I can.

UPDATE 1：

to make my codes/question more clear, I just want to make my codes as simple/clear as I can, that is why I want to use switch statement instead of if-else. Also, I heard that switch-statement is usually faster than if-else. (I am not 100% sure though).
I want to use switch-case because Case A, B, C are enum type. they are not variable. Sorry about the confusion.

each statements are more than 10 lines of codes. That is why I do not want to do the followings:

switch (enum variable) {
case A:
  statement1
  statement3
 break;
case B:
  statement2
  statement3
 break;

}

This code won't work, because Java 6 and older expects a value of a primitive type. Java 7 can dealt that with Strings. — Reporter
– Reporter, Commented Jul 23, 2013 at 15:48
switch is no good - you can't skip over cases, which is what you'd have to do to avoid coding the call to statement_3 twice — Bohemian
– Bohemian ♦, Commented Jul 23, 2013 at 15:49
what's wrong with if? If a switch is not the right tool, don't use it. Most of the time, it's not the right tool. — JB Nizet
– JB Nizet, Commented Jul 23, 2013 at 15:49
Or Replace Conditional with Polymorphism and get rid of the if / switch — zapl
– zapl, Commented Jul 23, 2013 at 15:54

Philipp Sander · Accepted Answer · 2013-07-23 16:41:52Z

26

i would recommend to define exactly what staments should be executed:

switch (variable){
    case A: 
        statement_1();
        statement_3();
        break;
    case B: 
        statement_2();
        statement_3();
        break;
}

for Update-3:

create methods for those 10 lines:

public void statement_1() {
    //your 10 lines of code
}

if you're always executing statement_3, except for case C you can go with if/else-blocks as you wrote them.

but in my honest opinion: define EXACTLY what has to be done in which case if you have a small amount of cases. it is easier to read for others

edited Jul 23, 2013 at 16:41

answered Jul 23, 2013 at 15:48

Philipp Sander

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Comments

jh314 · Accepted Answer · 2013-07-23 15:49:51Z

3

You can do this:

switch (variable){
  case A:  do statement_1; do statement_3; break;
  case B:  do statement_2; do statement_3; break;    
}

answered Jul 23, 2013 at 15:49

jh314

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Comments

Arthur Weborg · Accepted Answer · 2013-07-23 16:34:24Z

1

Why not nest the switch into the if statement? there is no-repeat code this way.

if(!C){
    statement_3;
    switch(variable){
    case A:
        statement_1;
        break;
    case B: 
        statement_2;
        break;
}

or make use of both the if-statement and the switch?

if(!C){
    statement_3;
}
switch(variable){
case A:
    statement_1;
    break;
case B: 
    statement_2;
    break;

edited Jul 23, 2013 at 16:34

answered Jul 23, 2013 at 16:08

Arthur Weborg

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2 Comments

Philipp Sander Over a year ago

but why use a switch with 2 cases and mix it all up? you don't gain performance or anything. it might be confusing for other developers

Arthur Weborg Over a year ago

Because the question referred to using a switch statement. If it is only 2 or 3 cases, then the if-elseif-else is the way to go. but if there is a grouping of statements that all share the same code, say a couple dozen times but not under one scenario, why repeat the code when you can have it executed before the switch (as long as a certain condition is not met)?

OldCurmudgeon · Accepted Answer · 2013-07-23 16:13:27Z

0

I often find introducing enums adds clarity. Here I imagine each enum is an issue which can be resolved through a number of processes:

enum Issue {
  A {
    void handleIt () {
      statement_1();
      statement_3();
    }
  },
  B {
    void handleIt () {
      statement_2();
      statement_3();
    }
  },
  C {
    void handleIt () {
      // Do nothing.
    }
  },
  D {
    void handleIt () {
      A.handleIt();
      B.handleIt();
    }
  };

  abstract void handleIt();
}

Note here that you get the added benefit of being able to handle certain issues using the solutions of other issues (see my D enum).

answered Jul 23, 2013 at 16:13

OldCurmudgeon

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Comments

Serhii Shevchyk · Accepted Answer · 2013-07-23 16:17:27Z

0

If a case has more than 2-3 statements it's bette(from point of view of readability and clean code) to extract them as separate methods:

switch (variable){
    case A: handleCaseA(); break;
    case B: handleCaseB(); break;
    default: handleDefaultCase(); break;
}

answered Jul 23, 2013 at 16:17

Serhii Shevchyk

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Comments

Tunaki · Accepted Answer · 2016-05-25 12:16:20Z

0

switch (variable) {
case A:  
do statement_1;
do statement_3;
break;
case B:
do statement_2;
do statement_3;
break;
}

edited May 25, 2016 at 12:16

Tunaki

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answered May 25, 2016 at 11:06

Sidarth

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1 Comment

Draken Over a year ago

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dreamcrash · Accepted Answer · 2021-03-18 21:26:49Z

0

With Java 12 switch-expressions you can do it nicely as follows:

switch (variable) {
        case A -> statement_1();
                  statement_3();
        case B -> statement_2();
                  statement_3();
};

edited Mar 18, 2021 at 21:26

answered Mar 16, 2021 at 8:20

dreamcrash

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Comments

Simas Joneliunas · Accepted Answer · 2020-01-15 07:39:12Z

When you use "case," use a switch statement first, and make sure you've got an initialized variable in it. Here's an example.

Use an initialized variable: i.e.

(String s=sc.nextLine();)

        switch (s) {
        case "Pepperoni":
            System.out.println("Pepperoni? Nice choice. Please wait............Ding! Here's your pepperoni pizza. Enjoy, and thanks for using the Local Pizzeria!");
        case "Cheese":
            System.out.println("Cheese? Okay! Soft cheese it is! Please wait............Ding! Here's your cheese pizza. Enjoy, and thank you for using the Local Pizzeria!");
            break;
        case "Mushrooms":
            System.out.println("Mushrooms? Veggie person, right? OK! Please wait............Ding! Here's your mushroom pizza. Enjoy, and thanks for using the Local Pizzeria!");
            break;
        case "Beef Bits":
            System.out.println("Beef bits? Like meat? Alright! Please wait............Ding! Here's your beef bit pizza. Enjoy, and thank you for using the Local Pizzeria!");

            break;
        case "Spicy Buffalo Chicken":
            System.out.println("Spicy buffalo chicken? Way to spice things up! Please wait............Ding! Here's your spicy buffalo chicken pizza. Enjoy, and thank you for using the Local Pizzeria!");
            break;
        case "Exit":
            System.out.println("See you soon!");
        }
    }

R.Nish · Accepted Answer · 2020-02-06 07:53:25Z

-2

Here u must use if statement in this way because in switch there are normally default value also.

    if (letter == 'A' || letter == 'B') { System.out.println("Statement 3 ");}

switch (letter) {
            case 'A':
                System.out.println("Statement 1 ");
                break;

            case 'B':
                System.out.println("Statement 2 ");
                break;

            case 'C':
                System.out.println();
                break;
            default:
                System.out.println("You entered wrong value");
}

edited Feb 6, 2020 at 7:53

answered Feb 26, 2018 at 13:29

R.Nish

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