Java doesn't recognize VectorList methods

Question

I get the following error trying to use Vector methods.
----jGRASP exec: javac -g /home/eugene/javafiles/book.java
book.java:20: cannot find symbol
symbol  : method elementAt(int)
location: interface java.util.List<java.lang.String>
               temp += author.elementAt( i ) + " ";
                             ^
1 error
----jGRASP wedge: exit code for process is 1.
----jGRASP: operation complete.
import java.util.*;
public class book
     private String title = "";
//     String author[] = new String[ 4 ];
/* Make author private */
     List<String> author = new Vector<String>();
     String publisher = "";
     int isbn = 0;
     double price = 0;
     int stock = 0;
/*  ---------------------------------------- HERE IS THE PROBLEM CODE --------------------------------------- */     
     String showAuthor()
          String temp = "";
          int i;
          for (i = 0; i < author.size(); i++)
               temp += author.elementAt( i ) + " ";
          return temp;     
     String showTitle()
          return title;
     void changeTitle( String input )
          title = input;
     String showPublisher()
          return publisher;
     void changePublisher( String input )
          publisher = input;
     int showIsbn()
          return isbn;
     void changeIsbn( int input )
          isbn = input;
     double showPrice()
          return price;
     void changePrice( double input )
          price = input;
     int showStock()
          return stock;
     void changeStock( int input )
          stock = input;
     book( String title, String publisher, int isbn, double price, int stock, String ... author )
          if ( author.length > 4 )
               throw new IllegalArgumentException( "You have too many authors" );
//          else if ( author.length == 0 )
//               throw new IllegalArgumentException( "You have no authors" );
          this.title = title;
          this.publisher = publisher;
          this.isbn = isbn;
          this.price = price;
          this.stock = stock;
          this.author = new ArrayList<String>( Arrays.asList( author ) );
     public static void main( String[] args )
          book test = new book( "title", "publisher", 123, 12.20, 4, "eugene", "vadim" );
          System.out.println( test.title );
}

Answer 1

yougene wrote:
     List<String> author = new Vector<String>();
Since you explicitly defined your reference to be of type List<String> you can only call methods that List has. And elementAt(int) is a method that's not existing in the List interface.
Use .get(int) instead.