Java Reflection calling constructor with primitive types

Question

I have a method in my test framework that creates an instance of a class, depending on the parameters passed in:

public void test(Object... constructorArgs) throws Exception {     Constructor<T> con;     if (constructorArgs.length > 0) {         Class<?>[] parameterTypes = new Class<?>[constructorArgs.length];         for (int i = 0; i < constructorArgs.length; i++) {             parameterTypes[i] = constructorArgs[i].getClass();           }         con = clazz.getConstructor(parameterTypes);     } else {         con = clazz.getConstructor();     } } 

The problem is, this doesn't work if the constructor has primitive types, as follows:

public Range(String name, int lowerBound, int upperBound) { ... }  .test("a", 1, 3); 

Results in:

java.lang.NoSuchMethodException: Range.<init>(java.lang.String, java.lang.Integer, java.lang.Integer) 

The primitive ints are auto-boxed in to object versions, but how do I get them back for calling the constructor?

Answer 1

Use Integer.TYPE instead of Integer.class.

As per the Javadocs, this is "The Class instance representing the primitive type int."

You can also use int.class. It's a shortcut for Integer.TYPE. Not only classes, even for primitive types you can say type.class in Java.