What is wrong with this switch statement?

Question

The following code returns an error, but I am not sure why. What needs to be changed to allow for compilation?

switch (DAO.class) {
    case BookDAO.class: 
        return bookDAO;
}

score 16 · Accepted Answer · edited May 23 '17 at 10:25

16

A switch works with the byte, short, char, and int primitive data types. It also works with enumerated types (and String from Java 7 onwards). NOT Class types.

DAO.class returns Class object of DAO

Refer this for what .class means

edited May 23 '17 at 10:25

Community

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answered Jul 10 '13 at 05:06

kosa

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@RiaD: I thought link will cover remaining things. – kosa Jul 10 '13 at 05:09
so then i have to use ifs ..great – osh Jul 10 '13 at 06:17

score 4 · Answer 2 · edited Jul 10 '13 at 05:09

4

From Java Docs

A switch works with the byte, short, char, and int primitive data types. It also works with enumerated types (discussed in Enum Types), the String class, and a few special classes that wrap certain primitive types: Character, Byte, Short, and Integer

More On this

edited Jul 10 '13 at 05:09

stinepike

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answered Jul 10 '13 at 05:09

Nargis

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score 3 · Answer 3 · answered Jul 10 '13 at 05:16

If you are using Java 7 - you can use switch statements with Strings. Then you could do something like this:

switch (DAO.class.getName()){
    case BookDAO.class.getName() : return bookDAO;
}

getName():

Returns the name of the entity (class, interface, array class, primitive type, or void) represented by this Class object, as a String.

score 2 · Answer 4 · answered Jul 10 '13 at 05:09

Here is the definition of the switch statement:

Unlike if-then and if-then-else statements, the switch statement can have a number of possible execution paths. A switch works with the byte, short, char, and int primitive data types. It also works with enumerated types (discussed in Enum Types), the String class, and a few special classes that wrap certain primitive types: Character, Byte, Short, and Integer (discussed in Numbers and Strings).

So it is not allowed Class type in the switch statement (Class classOfA = A.class;)

What is wrong with this switch statement?

4 Answers4