How to get the Array Class for a given Class in Java?

Question

I have a Class variable that holds a certain type and I need to get a variable that holds the corresponding array class. The best I could come up with is this:

Class arrayOfFooClass = java.lang.reflect.Array.newInstance(fooClass, 0).getClass(); 

Is there a way to do this without creating the new instance?

Answer 1

Since Java 12

Class provides a method arrayType(), which returns the array type class whose component type is described by the given Class. Please be aware that the individual JDK may still create an instance of that Class³.

Class<?> stringArrayClass = FooBar.arrayType() 

Before Java 12

If you don't want to create an instance, you could create the canonical name of the array manually and get the class by name:

// Replace `String` by your object type. Class<?> stringArrayClass = Class.forName(     "[L" + String.class.getCanonicalName() + ";" ); 

But Jakob Jenkov argues in his blog that your solution is the better one, because it doesn't need fiddling with strings.

Class<?> stringArrayClass = Array.newInstance(String.class, 0).getClass(); 

³ Thanks for the hint to Johannes Kuhn.

Answer 2

Since Java 12, there is the arrayType() method on java.lang.Class. With that:

Class<?> arrayOfFooClass = fooClass.arrayType(); 

---

The implementation of Class.arrayType() just calls Arrays.newInstance(this, 0).getClass().