如何在Java运行时通过使用类名获取类对象

Question

I am working on java,In run time I got class name but I want to create object for that class how can I do this any one help me. I tried below way please check my code below.

String emp = "Emp" // this is the classname i got in runtime(I will get dynamical this name)
Object obj = class.forName().newInstance();

up to this it is working fine ,but I got java.lang.Object in above code I don't want that object I want to convert that object into my className(Emp)object. like

Emp e =(Emp)obj;

Note: I am not sure every time I will get Emp classname at runtime total I have 100 Classes in myproject so any classname I will get here(like Emp,Dept,Student.....).

Answer 1

Maybe I don't understand your question, but if you are looking to create a class instance only using your class name, you can try this method:

public static MyClass getFromString(String myClassName) {
     Object result = null;
     MyClass final_result = null;

     try{
         result = Class.forName(myClassName).getConstructor().newInstance();
         final_result= (MyClass)result;
     }catch(ClassNotFoundException e){} //you must specify concrete Exception here

     return final_result; 
    }

Hope it helps.

Answer 2

It's not clear what you are trying to achieve. If you are confident that the class you loaded dynamically is Emp (or a subclass of it) it is sufficient to do the type cast like you did in your question. If you have doubts about the dynamically loaded type being compatible with Emp , because of the one hundred other classes you have, then it's not clear what you expect from us.

What you can do is to separate the type checking from the instantiation, eg

Class<? extends Emp> type = Class.forName(className).asSubclass(Emp.class);

Emp instance = type.newInstance();

This checks whether the type is compatible with Emp in the first line, thus the second line is guaranteed to return an instance of Emp .

However, the way, an incompatible type is reported does not change. It will be done by throwing a ClassCastException .

If that's not what you were asking for, you should reword your question.

Answer 3

Object object=Class.forName(className).getConstructor().newInstance();

Answer 4

  // Complete class name, including Package
  String name = "com.foo.Emp";

  Object object = Class.forName(name).getConstructor().newInstance();
  if (object instanceof Emp) {
     // Specific logic for Emp objects
  } else if (object instanceof Dept) {
     // Specific logic for Dept objects
  }

Hope it helps you