Exercise of he book Head First Java

[Frank Thuring]

Please can someone help me

I try to compile the code with the netbeans compiler

  package javaapplication2;

/**
 *
 * @author frank
 */
public class Main {
 class Books {
        String title;
        String author;
    }
    /**
     * @param args the command line arguments
     */
 class BooksTestDrive {
    public static void main(String[] args) {
         Books[]myBooks = new Books[3];
        int x = 0;
        myBooks[0]= new Books();
        myBooks[1]= new Books();
        myBooks[2]= new Books();

        myBooks[0].title = "The Grapes of Java";
        myBooks[1].title = "The Java Gatsby";
        myBooks[2].title = "The Java CookBook";
        myBooks[0].author = "Bob";
        myBooks[1].author = "Sue";
        myBooks[2].author = "Ian";

        while (x<3){
             System.out.print(myBooks[x].title) ;
                System.out.print("by");
              System.out.print(myBooks[x].author);
              x= x+ 1;
        }
    }
}
  

I got an error:
Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - non-static variable this cannot be referenced from a static context
at javaapplication2.Main.main(Main.java:23)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

It's the code of the book of head first java. can someone tell me what I am doing wrong?

[W. Joe Smith]

The code you posted is not what is in Head First Java. You have the Book and BooksTestDrive classes as inner classes to Main, which is not how it is on pg. 63, and I'm not even sure what you've posted will compile because you are missing a }.

[Frank Thuring]

Hi Joe,
I saw I missed a }
on page 68 of the second edition is the solution of the problem.
Now I got another error can you help me?

   * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package javaapplication2;

/**
 *
 * @author frank
 */
public class Main {
    class Books {
        String title;
        String author;
    }
    /**
     * @param args the command line arguments
     */ class BooksTestDrive {
        public static void main(String[] args) {
        Books [] myBooks = new Books[3];
        int x = 0;
        myBooks[0]= new Books();
        myBooks[1]= new Books();
        myBooks[2]= new Books();

        myBooks[0].title = "The Grapes of Java";
        myBooks[1].title = "The Java Gatsby";
        myBooks[2].title = "The Java CookBook";
        myBooks[0].author = "Bob";
        myBooks[1].author = "Sue";
        myBooks[2].author = "Ian";

            while (x<3){
                System.out.print(myBooks[x].title) ;
                System.out.print("by");
                System.out.print(myBooks[x].author);
                x= x+ 1;
            }//while
        }//public static void
    } // public class BooksTestDrive
}// public class main
  

the error is : java.lang.NoSuchMethodError: main
Exception in thread "main" Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

[W. Joe Smith]

I'm still confused as to why you have everything wrapped in a class called Main. It isn't needed, nor is it in the book. I'm not trying to be mean or anything, just trying to understand your thinking.

As for your error, from the command line run it as java BooksTestDrive. You should run the class that has the main method in it.

[Frank Thuring]

Hi Joe,
can you give me a clue with the main how you would programm this ?

[Frank Thuring]

Hi Joe,
can you give me a clue with the main how you would programm this ?

[W. Joe Smith]

Normal javaranch policy is to not give out code, but since this is from the book you are using, here is the code from HFJ:

 
class Books {   
        String title;   
        String author;   
}   
  

class BooksTestDrive {   
    public static void main(String[] args) {   
         Books [] myBooks = new Books[3];   
         int x = 0;   
         myBooks[0]= new Books();   
         myBooks[1]= new Books();   
         myBooks[2]= new Books();   
  
         myBooks[0].title = "The Grapes of Java";   
         myBooks[1].title = "The Java Gatsby";   
         myBooks[2].title = "The Java CookBook";   
         myBooks[0].author = "Bob";   
         myBooks[1].author = "Sue";   
         myBooks[2].author = "Ian";   

          while (x<3){   
             System.out.print(myBooks[x].title) ;   
             System.out.print("by");   
             System.out.print(myBooks[x].author);   
             x= x+ 1;   
         }
     } 
 } 
   

From there, I'd just compile it using javac <FileName>.java, then run it using java BooksTestDrive.

[Timothy Onggowasito]

I think it has something to do with netbean. They ussualy added the main class in the beginning as a template.
Try using Dr. Java as a compiler. It's much simpler to use.

[fred rosenberger]

If you're just learning how to write java code, throw away netbeans entirely and use the command line to compile.

[Frank Thuring]

I also think that netbeans is the problem. I will try Dr Java

[Campbell Ritchie]

Command Line, not Dr Java, please.