How to find the class a string describes in Java [duplicate]

Question

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Closed 9 years ago.

Possible Duplicate:
Class.getArrayType in Java?

I need to get the class for a type that is represented by a string. I am trying to invoke getMethod and I only have a list of strings for the types it requires.

Class.forName(str) works when str is a simple class, but not, for example, with an array like so:

Class<?>[] typeClasses = new Class<?>[]{Class.forName("my.type.class[]")};
Method method = someClass.getMethod(methodString, typeClasses);

Answer 1

One way to get hold of the Class object for an array type is to call getClass() on an array instance that you created reflectively; e.g.

Class someClass = Some.class;
Class someArrayClass = java.reflect.Array.newInstance(someClass, 0).getClass();

You can also use Class.forName() but you need to specify the class name in internal form; e.g. the class name for an Object[] is "[Ljava.lang.Object;". See Class.getName() for details of the class name format.

Answer 2

The problem is the string you're passing in the example is not the correct string representation of that class. This example code runs fine and prints true:

String[] array = new String[] { "hello" };
Class<?> arrayClass = array.getClass();
String stringClass = arrayClass.getName();
Class<?> parsedClass;
try {
    parsedClass = Class.forName(stringClass);
} catch (ClassNotFoundException e) {
    throw new RuntimeException(e);
}
System.out.println(arrayClass.equals(parsedClass));

See the Javadoc for Class#getName() for examples on how to represent array types as strings. If these strings are coming from somewhere else and you know what format to expect you could write a method to convert the strings into the format expected by the classloader.