Use string in switch case in java

Question

I need to change the following if s to a switch-case while checking for a String  to improve the cyclomatic complexity   String value   some methodx  if   apple  equals value         method1     if   carrot  equals value         method2     if   mango  equals value         method3     if   orange  equals value         method4      But I am not sure what value I m going to get

User · Answer

Everybody is using at least Java 7 now  right  Here is the answer to the original problem   String myString   getFruitString     switch  myString         case  apple           method1            break       case  carrot           method2            break       case  mango           method3            break       case  orange           method4            break      Notes   The case statements are equivalent to using String equals  As usual  String matching is case sensitive  According to the docs  this is generally faster than using chained if-else statements  as in cHao s answer

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Not very pretty but here is another way    String runFct            queryType equals  eq      method1           queryType equals  L L     method2           queryType equals  L R     method3           queryType equals  L LR     method4                method5   Method m   this getClass   getMethod runFct   m invoke this

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String name lname   name  JOptionPane showInputDialog null  Enter your name       lname  JOptionPane showInputDialog null  Enter your father name        if name equals  Ahmad            JOptionPane showMessageDialog null  welcome   name             if lname equals  Khan       JOptionPane showMessageDialog null  Name     name    nLast name    lname          else          JOptionPane showMessageDialog null  try again

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We can apply Switch just on data type compatible int  short Shor byte Byte int Integer char Character or enum type

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Learn to use else   Since value will never be equal to two unequal strings at once  there are only 5 possible outcomes -- one for each value you care about  plus one for  none of the above    But because your code doesn t eliminate the tests that can t pass  it has 16  possible  paths  2   the number of tests   of which most will never be followed   With else  the only paths that exist are the 5 that can actually happen   String value   some methodx  if   apple  equals value          method1    else if   carrot  equals value          method2    else if   mango  equals value          method3    else if   orance  equals value          method4      Or start using JDK 7  which includes the ability to use strings in a switch statement   Course  Java will just compile the switch into an if else like construct anyway

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Evaluating String variables with a switch statement have been implemented in Java SE 7  and hence it only works in java 7  You can also have a look at how this new feature is implemented in JDK 7

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Java 8 supports string switchcase   String type    apple    switch type       case  apple            statements     break      default           statements     break

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Java  before version 7  does not support String in switch case  But you can achieve the desired result by using an enum   private enum Fruit       apple  carrot  mango  orange     String value     assume input Fruit fruit   Fruit valueOf value      surround with try catch  switch fruit        case apple          method1          break      case carrot          method2          break         etc

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String value   someMethod    switch 0    default      if   apple  equals value             method1            break            if   carrot  equals value             method2            break            if   mango  equals value             method3            break            if   orance  equals value             method4            break

User · Answer

Here is a possible pre-1 7 way  which I can t recommend    public class PoorSwitch       final static public int poorHash  String s            long l   0L          for  char c  s toCharArray                   l   97 l   c                    return  int  l             public static void main  String args                  String param    foo           if  args length    1                        param   args 0                        uncomment these lines  to evaluate your hash            test   foo               test   bar            switch  poorHash  param                    this doesn t work  since you need a literal constant                so we have to evaluate our hash beforehand                 case poorHash   foo                  case 970596                    System out println   Foo                     break                               case poorHash   bar                  case 931605                    System out println   Bar                     break                            default                    System out println   unknown t    param                   break                                     public static void test  String s                System out println   Hash  t     s       t    poorHash  s              Maybe you could work with such a trick in a generated code  Else I can t recommend it  Not so much that the possibility of a hash collision makes me worry  but if something is mixed up  cut and paste   it is hard to find the error  931605 is not a good documentation    Take it just as proof of concept  as curiosity

User · Answer

Java does not support Switch-case with String  I guess this link can help you

User · Answer

To reduce cyclomatic complexity use a map   Map lt String Callable lt Object gt  gt  map   new HashMap  lt   gt        map   put    apple    new Callable lt Object gt       public Object call   method1       return null             map   get   x     call         or polymorphism

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Just to make concrete emory s answer  the executable code is the following      Map lt String Callable lt USer gt  gt  map   new HashMap lt String Callable lt User gt  gt       map put   test    new Callable lt User gt       public User call     return fillUser  test              map put   admin    new Callable lt Utente gt       public Utente call      return fillUser  admin              where user is a POJO  and then    User user   map get USERNAME  call      finally the called method is somewhere     private User fillUser String x                   User user   new User               set something in User         return user

[java] Use string in switch case in java

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