Class reflection : Class « Reflection « Java

1. Java
2. Reflection
3. Class

Class reflection

         

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

public class ShowClass {
  public static void main(String[] args) throws ClassNotFoundException {
    Class aClass = Class.forName("javax.swing.JComponent");
    if (aClass.isInterface()) {
      System.out.print(Modifier.toString(aClass.getModifiers()) + " "
          + typeName(aClass));
    } else if (aClass.getSuperclass() != null) {
      System.out.print(Modifier.toString(aClass.getModifiers()) + " class "
          + typeName(aClass) + " extends " + typeName(aClass.getSuperclass()));
    } else {    
      System.out.print(Modifier.toString(aClass.getModifiers()) + " class "
          + typeName(aClass));
    }

    Class[] interfaces = aClass.getInterfaces();
    if ((interfaces != null) && (interfaces.length > 0)) {
      if (aClass.isInterface())
        System.out.print(" extends ");
      else
        System.out.print(" implements ");
      for (int i = 0; i < interfaces.length; i++) {
        if (i > 0)
          System.out.print(", ");
        System.out.print(typeName(interfaces[i]));
      }
    }

    System.out.println(" {");

    Constructor[] constructors = aClass.getDeclaredConstructors();
    for (int i = 0; i < constructors.length; i++)
      printMethodOrConstructor(constructors[i]);

    Field[] fields = aClass.getDeclaredFields(); 
    for (int i = 0; i < fields.length; i++)
      printField(fields[i]);

    Method[] methods = aClass.getDeclaredMethods(); 
    for (int i = 0; i < methods.length; i++)
      printMethodOrConstructor(methods[i]);

    System.out.println("}"); 
  }

  public static String typeName(Class t) {
    String brackets = "";
    while (t.isArray()) {
      brackets += "[]";
      t = t.getComponentType();
    }
    String name = t.getName();
    int pos = name.lastIndexOf('.');
    if (pos != -1)
      name = name.substring(pos + 1);
    return name + brackets;
  }

  public static String modifiers(int m) {
    if (m == 0)
      return "";
    else
      return Modifier.toString(m) + " ";
  }

  public static void printField(Field f) {
    System.out.println("  " + modifiers(f.getModifiers())
        + typeName(f.getType()) + " " + f.getName() + ";");
  }

  public static void printMethodOrConstructor(Member member) {
    Class returntype = null, parameters[], exceptions[];
    if (member instanceof Method) {
      Method m = (Method) member;
      returntype = m.getReturnType();
      parameters = m.getParameterTypes();
      exceptions = m.getExceptionTypes();
      System.out.print("  " + modifiers(member.getModifiers())
          + typeName(returntype) + " " + member.getName() + "(");
    } else {
      Constructor c = (Constructor) member;
      parameters = c.getParameterTypes();
      exceptions = c.getExceptionTypes();
      System.out.print("  " + modifiers(member.getModifiers())
          + typeName(c.getDeclaringClass()) + "(");
    }

    for (int i = 0; i < parameters.length; i++) {
      if (i > 0)
        System.out.print(", ");
      System.out.print(typeName(parameters[i]));
    }
    System.out.print(")");
    if (exceptions.length > 0)
      System.out.print(" throws ");
    for (int i = 0; i < exceptions.length; i++) {
      if (i > 0)
        System.out.print(", ");
      System.out.print(typeName(exceptions[i]));
    }
    System.out.println(";");
  }
}

           
         
    
    
    
    
    
    
    
    
  

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