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read java file

Posted on 2000-05-15
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Last Modified: 2008-02-20
i`m trying to write a program that able to read a java file
and output a result to tell how many methods in the particular file.
for example:

public class Hello
{
     int x;
     Hello()
     {
 
     }

     public static void main(String args[ ])
     {    

     }

      public void A( )
      {

      }

      public void B()
      {

       }

}
output: 4 methods
-Hello
-main
-A
-B

can anyone please tell me how to to do?
0
Comment
Question by:wongww
  • 8
  • 4
12 Comments
 
LVL 7

Expert Comment

by:Ravindra76
ID: 2813207
It will list Object methods also.

I will send later another version

import java.lang.reflect.*;

class GetMethods {

      public static void main(String args[]){
            
            try {      
                  Hello obj = new Hello();
                  Class hello = obj.getClass();
                  Method methods[] = hello.getMethods();
                  for ( int i=0; i < methods.length; i++ ) {                  
                        System.out.println("Method "+(i+1)+"="+methods[i]);
                  }
            }
            catch ( Exception ee){
                  ee.printStackTrace();
            }
      }
}
0
 
LVL 7

Expert Comment

by:Ravindra76
ID: 2813223
import java.lang.reflect.*;

class GetMethods {

      public static void main(String args[]){
            
            try {      
                  Hello obj = new Hello();
                  Class hello = obj.getClass();
                  String cname = hello.getName();
                  System.out.println("Class Name="+cname);
                  
                  Constructor constructors[] = hello.getConstructors();
                  System.out.println("Constructors="+constructors.length);
                  for ( int i=0; i <  constructors.length; i++ ) {
                        String cons = constructors[i].toString();
                  //      if ( cons.indexOf(cname) > 0)                  
                        System.out.println("Constructor "+(i+1)+"="+cons);
      
                  }

                  
                  Method methods[] = hello.getMethods();                  
      
                  for ( int i=0; i < methods.length; i++ ) {
                        String method = methods[i].toString();
                        if ( method.indexOf(cname) > 0)                  
                        System.out.println("Method "+(i+1)+"="+method);
                  }
            }
            catch ( Exception ee){
                  ee.printStackTrace();
            }
      }
}
0
 
LVL 7

Expert Comment

by:Ravindra76
ID: 2813227

Read documentation for

java.lang.Class and  java.lang.reflect package
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LVL 7

Expert Comment

by:Ravindra76
ID: 2813230
Ok.

From the output it is sure that

Java Interpreter is not treating

default constructor ( Hello () ) as a constructor.

That's why You got zero constructors
0
 
LVL 7

Expert Comment

by:Ravindra76
ID: 2813234
ravindra76 changed the proposed answer to a comment
0
 
LVL 7

Accepted Solution

by:
Ravindra76 earned 600 total points
ID: 2813240
Chagne Hello.java as



public class Hello
{
int x;
public Hello()
{

}


public static void main(String args[ ])
{

}

public void A( )
{

}

public void B()
{

}

}

The reason why Hello() not came  in previous comment is:-

 An array of length 0 is returned if the
     class has no public constructors, or if the class is an array class, or
     if the class reflects a primitive type or void.



0
 

Author Comment

by:wongww
ID: 2813327
i have one problem!!My program have to open ANY type of standard .java file to read it using FileDialog.
In ur program u have declare an object for the particular class that u wanted to read.How can I do that in my case??
0
 
LVL 7

Expert Comment

by:Ravindra76
ID: 2813674
import java.lang.reflect.*;
import java.lang.*;

class GetMethods {

      public static void main(String args[]){
            
            try {      
                  
                  Class hello = Class.forName(args[0]);
                  String cname = hello.getName();
                  System.out.println("Class Name="+cname);
                  
                  Constructor constructors[] = hello.getConstructors();
                  System.out.println("Constructors="+constructors.length);
                  for ( int i=0; i <  constructors.length; i++ ) {
                        String cons = constructors[i].toString();
                  //      if ( cons.indexOf(cname) > 0)                  
                        System.out.println("Constructor "+(i+1)+"="+ constructors[i].getName());
      
                  }

                  
                  Method methods[] = hello.getMethods();                  
      
                  for ( int i=0; i < methods.length; i++ ) {
                        String method = methods[i].toString();
                        if ( method.indexOf(cname) > 0)                  
                        System.out.println("Method "+(i+1)+"="+methods[i].getName());
                  }
            }
            catch ( Exception ee){
                  ee.printStackTrace();
            }
      }
}
/*
java.io.File has getName() function.

Get the file name and substitute it in the palce of args[0]

That's all

:)*/
0
 

Author Comment

by:wongww
ID: 2816262
I have follow ur code.But it is not working!!Got run time error. Can u please tell me why??
Heres my code:


import java.lang.reflect.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.lang.*;
import java.util.*;

public class Display extends Frame implements ActionListener
{

     int num_arr;
     int num_array;
     String filename;


   public Display() //constructor
   {
        super();
        setSize(400,300);
        setTitle("");
        addWindowListener(new WindowDestroyer());

        Menu mb = new Menu("File");
        MenuItem m;
        m = new MenuItem("Open");
        m.addActionListener(this);
        mb.add(m);
        m = new MenuItem("Close");
        m.addActionListener(this);
        mb.add(m);
        m = new MenuItem("Exit");
        m.addActionListener(this);
        mb.add(m);


        MenuBar mBar = new MenuBar();
        mBar.add(mb);

        setMenuBar(mBar);
   }


    public void actionPerformed(ActionEvent e)
    {
        try
        {
       String actionCommand = e.getActionCommand();
       Dialog dl;
       Label l;

       if(actionCommand.equals("Open"))
       {
          FileDialog fd=new FileDialog(f,"Open Image file",FileDialog.LOAD);
          fd.setVisible(true);
          String fname=fd.getFile();
          String fdir=fd.getDirectory();
          String fn=fd.getName();
   
          if((fname!=null && fname.indexOf(".JAVA")>0) || (fname!=null && fname.indexOf(".java")>0))
          {
              try{

               Class hello = Class.forName(fn);
               String cname = hello.getName();
               System.out.println("Class Name="+cname);
     
               }


              catch ( Exception ee){
              ee.printStackTrace();
              }
         }
        } //end if
        else if(actionCommand.equals("Close"))
        {
           

        } //end if

        else if(actionCommand.equals("Exit"))
        {
           System.exit(0);
        } // end if



 

        } catch (NullPointerException e1) {}
    }
         
   


  public static void main(String[] args)
  {
     f=new Display();
     f.setVisible(true);
     f.setTitle("DISPLAY");
   }//end main

   static Display f = new Display();
   Panel center=new Panel();


 }//end class
0
 
LVL 7

Expert Comment

by:Ravindra76
ID: 2820030
The correct version:_


import java.lang.reflect.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.lang.*;
import java.util.*;

public class Display extends Frame implements ActionListener
{

     int num_arr;
     int num_array;
     String filename;


   public Display() //constructor
   {
        super();
        setSize(400,300);
        setTitle("");
        //addWindowListener(new WindowDestroyer());

        Menu mb = new Menu("File");
        MenuItem m;
        m = new MenuItem("Open");
        m.addActionListener(this);
        mb.add(m);
        m = new MenuItem("Close");
        m.addActionListener(this);
        mb.add(m);
        m = new MenuItem("Exit");
        m.addActionListener(this);
        mb.add(m);


        MenuBar mBar = new MenuBar();
        mBar.add(mb);

        setMenuBar(mBar);
   }


    public void actionPerformed(ActionEvent e)
    {
        try
        {
       String actionCommand = e.getActionCommand();
       Dialog dl;
       Label l;

       if(actionCommand.equals("Open"))
       {
          FileDialog fd=new FileDialog(f,"Open Image file",FileDialog.LOAD);
          fd.setVisible(true);
          String fname=fd.getFile();
          fname = fname.substring(0,fname.length()-5);            
          System.out.println("File name="+fname);                        
   
          if(fname!=null )
          {
              try{

               Class hello = Class.forName(fname);
               String cname = hello.getName();
               System.out.println("Class Name="+cname);
     
               }


              catch ( Exception ee){
              ee.printStackTrace();
              }
         }
        } //end if
        else if(actionCommand.equals("Close"))
        {
           

        } //end if

        else if(actionCommand.equals("Exit"))
        {
           System.exit(0);
        } // end if



 

        } catch (NullPointerException e1) {}
    }
         
     


  public static void main(String[] args)
  {
     f=new Display();
     f.setVisible(true);
     f.setTitle("DISPLAY");
   }//end main

   static Display f = new Display();
   Panel center=new Panel();


 }//end class



/* IMPORTANT:-The file You are selecting must be compiled before U run this program.
  Because we are loading the Class object
which will execute when THe .java file is
  compiled...SO be sure that , the file u are selecting from FileDialog must be compiled
      and .class file should be present in same directory.:)

 In the code , You selected .java file from Dialog. But be sure that .class should be present
  for that .java file.

If You select .class file directly in filedialog,
Replace

          fname = fname.substring(0,fname.length()-5);            

with
            fname = fname.substring(0,fname.length()-6);            

*/

:)
0
 

Author Comment

by:wongww
ID: 2820222
Thankz!
0
 

Author Comment

by:wongww
ID: 2820223
Adjusted points from 100 to 150
0

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