CODEWITHSUNDEEP
javatype-conversion
Zlopez
Zlopez

Reputation: 700

How to do type conversion by string?

i have class type saved in string like this:

String cls = "Test";

Here is some code i tried:

String cls = "Test";

Object obj = new Test();

Test test = (Class.forName(cls)) obj;

But it ends with compilation error:

Main.java:21: error: ';' expected
        Test test = (Class.forName(cls)) obj;

How can I use this string for type conversion?

PS: Presume I don't know what type obj is, I only have String cls.

Upvotes: 0

Views: 105

Answers (5)

Johnny
Johnny

Reputation: 1383

    String cls = "Test";

    Test t = new Test();

    OtherTest ot = new OtherTest();

    Class<?> c = Class.forName(cls);

    if(t.getClass() == c) {
        System.out.println("Hooray!");
    }

    if(ot.getClass() == c) {
        System.out.println("Mmmmh");
    }

It prints out "Hooray"

Is this what you want?

Upvotes: 0

Erwin de Gier
Erwin de Gier

Reputation: 662

You can use the cast method on the Class you created from the String:

String className = "Test";
Class<?> clz = Class.forName(className);
clz.cast(objectToBecasted);

Upvotes: 1

Johnny
Johnny

Reputation: 1383

Ok,

Try this:

Test test = (Test) Class.forName(cls).cast(obj);

Upvotes: 0

Florian Schaetz
Florian Schaetz

Reputation: 10652

If you want to instantiate a class for which you have the name, you were already on the right track:

// Remember that this class name tells us, it's in the default package, 
// otherwise you would have to use the fully qualified name, for example
// com.mydomain.Test

String className = "Test";

// First we need to get the correct class object

Class<?> clz = Class.forName(className);

// And from this class object, we can create a new instance, in other
// words, a "Test" object:

Test test = (Test)clz.newInstance();

Of course, there are some exceptions that have to be caught (or declared), etc. But I think you get the idea. If you do not want to call the default constructor (the one with no arguments, in other words the equivalent of new Test() ) of your "Test" class, you would have to search the right constructors via the appropriate methods of the Class object (getDeclaredConstructor, etc.etc. - see the API doc for that).

Upvotes: 2

Neeraj Jain
Neeraj Jain

Reputation: 7730

java.lang.class.Class c=Class.forName("ClassNameToBeLoadedDynamically") is not required as

A call to Class.forName("X") causes the class named X to be dynamically loaded (at runtime).

You can directly use 

Test test = (Test) obj;

Upvotes: 0

Related Questions