Java에서 클래스를 매개 변수로 어떻게 전달합니까?

Java에서 클래스를 매개 변수로 어떻게 전달합니까?

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Java에서 클래스를 매개 변수로 전달하고 해당 클래스에서 일부 메소드를 실행하는 방법이 있습니까?

void main()
{
    callClass(that.class)
}

void callClass(???? classObject)
{
    classObject.somefunction
    // or 
    new classObject()
    //something like that ?
}

Google Web Toolkit을 사용하고 있으며 반영을 지원하지 않습니다.

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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);
        }
    }

• Reflection API에 대한 좋은 예는 다음과 같습니다.

리플렉션을 사용하여 메소드를 호출하는 방법

 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);
         }
      }
   }

참조

• 자바 리플렉션

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

메소드를 호출하려면 다음과 같이 호출하십시오.

callingMethod(ClassBeingCalled.class);

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사용하다

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

A Class도 Java 객체이므로 해당 유형을 사용하여 참조 할 수 있습니다.

공식 문서 에서 자세한 내용을 읽으십시오 .

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이런 일은 쉽지 않습니다. 정적 메소드를 호출하는 메소드는 다음과 같습니다.

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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업데이트 : 잠깐, 질문에서 gwt 태그를 보았습니다. GWT에서는 리플렉션을 사용할 수 없습니다

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I am not sure what you are trying to accomplish, but you may want to consider that passing a class may not be what you really need to be doing. In many cases, dealing with Class like this is easily encapsulated within a factory pattern of some type and the use of that is done through an interface. here's one of dozens of articles on that pattern: http://today.java.net/pub/a/today/2005/03/09/factory.html

using a class within a factory can be accomplished in a variety of ways, most notably by having a config file that contains the name of the class that implements the required interface. Then the factory can find that class from within the class path and construct it as an object of the specified interface.

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As you said GWT does not support reflection. You should use deferred binding instead of reflection, or third party library such as gwt-ent for reflection suppport at gwt layer.

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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.

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Se these: http://download.oracle.com/javase/tutorial/extra/generics/methods.html

here is the explaniation for the template methods.

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Have a look at the reflection tutorial and reflection API of Java:

https://community.oracle.com/docs/DOC-983192enter link description here

and

http://docs.oracle.com/javase/6/docs/api/java/lang/Class.html

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Class as paramater. Example.

Three classes:

class TestCar {

    private int UnlockCode = 111;
    protected boolean hasAirCondition = true;
    String brand = "Ford";
    public String licensePlate = "Arizona 111";
}

--

class Terminal {

public void hackCar(TestCar car) {
     System.out.println(car.hasAirCondition);
     System.out.println(car.licensePlate);
     System.out.println(car.brand);
     }
}

--

class Story {

    public static void main(String args[]) {
        TestCar testCar = new TestCar();
        Terminal terminal = new Terminal();
        terminal.hackCar(testCar);
    }

}

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In class Terminal method hackCar() take class TestCar as parameter.

참고URL : https://stackoverflow.com/questions/4872978/how-do-i-pass-a-class-as-a-parameter-in-java