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.<

Answer 1

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.

Answer 2

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

Answer 3

Java 8 supports string switchcase.

String type = "apple";

switch(type){
    case "apple":
       //statements
    break;
    default:
       //statements
    break; }

Answer 4

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

Answer 5

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.

Answer 6

To reduce cyclomatic complexity use a map:

Map<String,Callable<Object>> map = new HashMap < > ( ) ;
map . put ( "apple" , new Callable<Object> () { public Object call ( method1 ( ) ; return null ; } ) ;
...
map . get ( x ) . call ( ) ;

or polymorphism