Using filenames to create a class

Question

hello everybody!!
i wanto to know something i've read into some docs (i dont remember where) some time ago...
i read that we can create an instance of a class at runtime having only the filename (.class) of the class. for example, i wanto to create a function like this:
public Object createByFile(String classFileName)
Object xyz = new Object();
xyz = functionToCreate(classFileName);
is there any way that i can do that? i'm working on an application where i won�t know what class i'll have to instantiate at coding time
thanx in advance

Answer 1

You can easily create an instance of a class by name. Using the class name (without the .class) you can call the following code.
Class newClass = Class.forName( className );
Object myObject = newClass.newInstance();
Note that the above code will only work if there is a constructor which does not take any parameters. To create a class that contains a constructor that takes parameters you must locate the constructor using something like this:
Class parameterTypes[] = new Class[] { java.lang.String.class };
Constructor myConstructor = newClass.getConstructor( parameterTypes );
then using the constructor call the newInstance method of the constructor passing an object array of the same parameter types defined above:
Object myArray[] = new Object[] { "Test String" }
myObject = myConstructor.newInstance( myArray );
See the getConstructor() documentation on the Class object and the newInstance() method of the Constructor object for a little more help on the parameters
myObject = myConstructor.newInstance( new Object[] { "Test String" } );