• Reference material
  • Java core technology Volume 1
• java provides a very rich library for reflection
  • Purpose of reflection
    • Dynamic operation Java code program
    • Analysis class in operation
    • Querying objects at run time
    • Implementation of general array operation code
    • Using the method object
  • The reflection mechanism is powerful and complex, which is used by program builders. Good use can also be used to analyze the java underlying layer.
  • Class Class
    • Class is a subclass of Object, but it is not an Object. It is a type. It's not an Object concept like a basic type.
    • The Object class directly calls getClass and returns an instance of Class type
  • Code example

    •         //If the class path or name is wrong, it will explode and no such exception can be found
              // String className = "java.util.DateNONONONO";
              // java.lang.ClassNotFoundException: java.util.Datenonono
              // at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
              // at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
              // at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:338)
              // at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
              // at java.lang.Class.forName0(Native Method)
              // at java.lang.Class.forName(Class.java:264)
              // at com.testservice.Demo001.main(Demo001.java:13)
      
              //Date class
              String className = "java.util.Date";
      
              try {
                  //Generate a mine based on the package name class name
                  Class<?> dataClass = Class.forName(className);
                  //Print the name of the Date
                  System.out.println("dataClass.getName() = " + dataClass.getName());
                  //Output dataClass.getName() = java.util.Date
      
                  //Call the api of Class to create a default construction instance of this object
                  Object obj = dataClass.newInstance();
      
                  //Forced conversion to date
                  Date dateObj = (Date) obj;
      
                  //Call the method output to see if it works
                  long time = dateObj.getTime();
                  System.out.println("time = " + time);
                  //Output time = 1536371161364
      
                  System.out.println(dataClass.getName() + ">>" + dataClass.getClass().getName());
                  //Output Java. Util. Date > > java. Lang.class
      
              } catch (ClassNotFoundException e) {
                  e.printStackTrace();
              } catch (IllegalAccessException e) {
                  e.printStackTrace();
              } catch (InstantiationException e) {
                  e.printStackTrace();
              }

       

To write TODO