Java Using Strings as Code

Question

Okay, so, here's what I have in code:

public void makeObject(int i){
    String s = getString(i); //This returns the name of a class
    new s(); //This is what I want to do
}

Can I do this?

Do you just want to create a new instance of an already-existing class? Then look at Class.forName which will return a Class. — mpnk121
– mpnk121, Commented Jun 25, 2011 at 7:45
Why are you doing this? For sending messages across a network? — BlueRaja - Danny Pflughoeft
– BlueRaja - Danny Pflughoeft, Commented Jun 25, 2011 at 8:22

Roy T. · Accepted Answer · 2011-06-25 07:50:57Z

9

No you can't do this, but what you're probably looking for is called 'reflection'.

Look at these series of (free) slides: http://www.slideshare.net/CiaranMcHale/java-reflection-explained-simply especially slide 11, but read the ones before that as well. It will give you an idea of what reflection is and a way to make a class by knowing the name (as a string) and how to instantiate a new instance of that class.

You can also find methods and fields by name, you can even modify existing classes in code.

Edit: for example the following code will return a class by string name

Class cls = Class.ForName("MyPackage.MyClassName");
return cls.NewInstance();

answered Jun 25, 2011 at 7:50

Roy T.

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1 Comment

Brandon oubiub Over a year ago

Thanks, haven't looked at it yet, but I think it is perfect by how you described it.

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