How do I pass a class as a parameter in Java?

Question

public void foo(Class c){
        try {
            Object ob = c.newInstance();
        } catch (InstantiationException ex) {
            Logger.getLogger(App.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            Logger.getLogger(App.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

• Here are some good examples on Reflection API

How to invoke method using reflection

 import java.lang.reflect.*;


   public class method2 {
      public int add(int a, int b)
      {
         return a + b;
      }

      public static void main(String args[])
      {
         try {
           Class cls = Class.forName("method2");
           Class partypes[] = new Class[2];
            partypes[0] = Integer.TYPE;
            partypes[1] = Integer.TYPE;
            Method meth = cls.getMethod(
              "add", partypes);
            method2 methobj = new method2();
            Object arglist[] = new Object[2];
            arglist[0] = new Integer(37);
            arglist[1] = new Integer(47);
            Object retobj 
              = meth.invoke(methobj, arglist);
            Integer retval = (Integer)retobj;
            System.out.println(retval.intValue());
         }
         catch (Throwable e) {
            System.err.println(e);
         }
      }
   }

Also See

• Java Reflection

public void callingMethod(Class neededClass) {
    //Cast the class to the class you need
    //and call your method in the class
    ((ClassBeingCalled)neededClass).methodOfClass();
}

To call the method, you call it this way:

callingMethod(ClassBeingCalled.class);

Construct your method to accept it-

public <T> void printClassNameAndCreateList(Class<T> className){
    //example access 1
    System.out.print(className.getName());

    //example access 2
    ArrayList<T> list = new ArrayList<T>();
    //note that if you create a list this way, you will have to cast input
    list.add((T)nameOfObject);
}

Call the method-

printClassNameAndCreateList(SomeClass.class);

You can also restrict the type of class, for example, this is one of the methods from a library I made-

protected Class postExceptionActivityIn;

protected <T extends PostExceptionActivity>  void  setPostExceptionActivityIn(Class <T> postExceptionActivityIn) {
    this.postExceptionActivityIn = postExceptionActivityIn;
}

For more information, search Reflection and Generics.

Use

void callClass(Class classObject)
{
   //do something with class
}

A Class is also a Java object, so you can refer to it by using its type.

Read more about it from official documentation.

This kind of thing is not easy. Here is a method that calls a static method:

public static Object callStaticMethod(
    // class that contains the static method
    final Class<?> clazz,
    // method name
    final String methodName,
    // optional method parameters
    final Object... parameters) throws Exception{
    for(final Method method : clazz.getMethods()){
        if(method.getName().equals(methodName)){
            final Class<?>[] paramTypes = method.getParameterTypes();
            if(parameters.length != paramTypes.length){
                continue;
            }
            boolean compatible = true;
            for(int i = 0; i < paramTypes.length; i++){
                final Class<?> paramType = paramTypes[i];
                final Object param = parameters[i];
                if(param != null && !paramType.isInstance(param)){
                    compatible = false;
                    break;
                }

            }
            if(compatible){
                return method.invoke(/* static invocation */null,
                    parameters);
            }
        }
    }
    throw new NoSuchMethodException(methodName);
}

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Update: Wait, I just saw the gwt tag on the question. You can't use reflection in GWT