Create new object from a string in Java

Yes, you can load a class on your classpath given the String name using reflection, using Class.forName(name), grabbing the constructor and invoking it. I'll do you an example.

Consider I have a class:

com.crossedstreams.thingy.Foo

Which has a constructor with signature:

Foo(String a, String b);

I would instantiate the class based on these two facts as follows:

// Load the Class. Must use fully qualified name here!
Class clazz = Class.forName("com.crossedstreams.thingy.Foo");

// I need an array as follows to describe the signature
Class[] parameters = new Class[] {String.class, String.class};

// Now I can get a reference to the right constructor
Constructor constructor = clazz.getConstructor(parameters);

// And I can use that Constructor to instantiate the class
Object o = constructor.newInstance(new Object[] {"one", "two"});

// To prove it's really there...
System.out.println(o);

Output:

com.crossedstreams.thingy.Foo@20cf2c80

There's plenty of resources out there which go into more detail about this, and you should be aware that you're introducing a dependency that the compiler can't check for you - if you misspell the class name or anything, it will fail at runtime. Also, there's quite a few different types of Exception that might be throws during this process. It's a very powerful technique though.

This should work:

import java.lang.reflect.*;

FirstArgType arg1;
SecondArgType arg2;
Class cl = Class.forName("TheClassName");
Constructor con = cl.getConstructor(FirstArgType.class, SecondArgType.class);
Object obj = con.newInstance(arg1, arg2);

From there you can cast to a known type.

This is what you want to do:

String className = "Class1";
Object xyz = Class.forName(className).newInstance();

Note that the newInstance method does not allow a parametrized constructor to be used. (See Class.newInstance documentation)

If you do need to use a parametrized constructor, this is what you need to do:

import java.lang.reflect.*;

Param1Type param1;
Param2Type param2;
String className = "Class1";
Class cl = Class.forName(className);
Constructor con = cl.getConstructor(Param1Type.class, Param2Type.class);
Object xyz = con.newInstance(param1, param2);

See Constructor.newInstance documentation

This worked a little more cleanly for me in JDK7, while the answers above made things a bit more difficult than they needed to be from a newbie perspective: (assumes you've declared 'className' as a String variable passed as a method parameter or earlier in the method using this code):

Class<?> panel = Class.forName( className );
JPanel newScreen = (JPanel) panel.newInstance();

From this point you can use properties / methods from your dynamically-named class exactly as you would expect to be able to use them:

JFrame frame = new JFrame(); // <<< Just so no-one gets lost here
frame.getContentPane().removeAll();
frame.getContentPane().add( newScreen );
frame.validate();
frame.repaint();

The examples in other answers above resulted in errors when I tried to .add() the new 'Object' type object to the frame. The technique shown here gave me a usable object with just those 2 lines of code above.

Not exactly certain why that was - I'm a Java newbie myself.