How do I pass a class as a parameter in Java

Question

Is there any way to pass class as a parameter in Java and fire some methods from that class   void main         callClass that class     void callClass      classObject        classObject somefunction        or      new classObject         something like that       I am using Google Web Toolkit and it does not support reflection

User · Answer

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

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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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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 lt   gt  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 lt   gt    paramTypes   method getParameterTypes                if parameters length    paramTypes length                   continue                            boolean compatible   true              for int i   0  i  lt  paramTypes length  i                     final Class lt   gt  paramType   paramTypes i                   final Object param   parameters i                   if param    null  amp  amp   paramType isInstance param                        compatible   false                      break                                               if compatible                   return method invoke    static invocation   null                      parameters                                     throw new NoSuchMethodException methodName         Update   Wait  I just saw the gwt tag on the question  You can t use reflection in GWT

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Construct your method to accept it-  public  lt T gt  void printClassNameAndCreateList Class lt T gt  className         example access 1     System out print className getName            example access 2     ArrayList lt T gt  list   new ArrayList lt T gt           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  lt T extends PostExceptionActivity gt   void  setPostExceptionActivityIn Class  lt T gt  postExceptionActivityIn        this postExceptionActivityIn   postExceptionActivityIn      For more information  search Reflection and Generics

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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                      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

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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        To call the method  you call it this way   callingMethod ClassBeingCalled class

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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                In class Terminal method hackCar   take class TestCar as parameter

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Se these  http   download oracle com javase tutorial extra generics methods html  here is the explaniation for the template methods

User · Answer

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

User · Answer

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

[java] How do I pass a class as a parameter in Java?

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