How to parse String to an object

Question

First of all, I've already searched around a bit, but couldn't really find an answer for my problem. If such a thread alreay exists, I'm sorry. Also, I'm only at a beginner's level, so maybe i just didn't understand what was being explained and maybe I don't use the right terminology.

I want to parse a String to an object type. For example:

Boat boat1 = new Motorboat();
String type = JOptionPane.showInputDialog(null, "Enter a type");
if(boat1 instanceof type)
{
    System.out.println("boat1 is a motorboat");
}

Boat is an abstract class and Motorboat is one of its subclasses.

I know this won't work, because type is a String, but how can i make this work? How can i parse this String to an object type?

Thanks in advance.

Minor point: You are (I believe) wanting to convert a string to a class, not an object of the class. (A String already is an object.) — Hot Licks
– Hot Licks, Commented Dec 1, 2013 at 14:05

Domi · Accepted Answer · 2013-12-01 13:58:35Z

3

You can lookup a Class object from a string with Class.forName:

String typeName = JOptionPane.showMessageDialog(null, "Enter a type");
Class<?> class = Class.forName(typeName);
if (class != null && class.isInstance(boat1))
{
    System.out.println("boat1 is a motorboat");
}

Pay special attention though because your comparison requires a fully qualified classname (that includes all packages).

answered Dec 1, 2013 at 13:58

Domi

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2 Comments

user3054461 Over a year ago

That works so far, but now I want to parse boat1 to the type that the user has given. What I want is: Motorboat boat2 = (type) boat1; That still doesn't work.

Domi Over a year ago

@user3054461 Use Class.cast

eugene82 · Accepted Answer · 2013-12-01 13:58:21Z

1

Try using the class of your object:

if (boat1.getClass().getSimpleName().equals(type)) {
    System.out.println("boat1 is a motorboat");
}

answered Dec 1, 2013 at 13:58

eugene82

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