How do I declare an arrayList and initilise it in a constructor Method

[lupercal hill]

I am trying to extend wordRecord class by Record, record will be used to write randomly to disk.

I am having problems with using arrayLists. Can you please tell me what Im doing wrong. How do I declare an arrayList and initilise it in a constructor Method.

My code is below

Record class

 
 
// Record class for the RandomAccessFile programs.
import java.util.ArrayList;
import java.io.*;
public class Record extends wordRecord {
 
  
   public Record()
   {
      this( 0,0,0, "", "", null);// i used null because I dont know better
   }
 
   public Record( int correctAttempts, int incorrectAttempts, int location, String englishWord,
                  String foreignWord, ArrayList categories )
   {
      super( correctAttempts, incorrectAttempts, location, englishWord, foreignWord, categories ); // this just doesnt work.
   }
 

wordRecord class

 import java.util.ArrayList;
/**
 * Write a description of class wordObject here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class wordRecord
{
    // instance variables - replace the example below with your own
   
    private int correctAttempts;
    private int incorrectAttempts;
    private int location;
    private String englishWord;
    private String foreignWord;
    private ArrayList categories = new ArrayList();
    
    
    /**
     * Constructor for objects of class wordObject
     */
    public wordRecord()
    {
        // initialise instance variables
       
    
    correctAttempts= 0;
    incorrectAttempts= 0;
    location= 0;
    englishWord= "";
    foreignWord= "";
    categories.add(0);
    }
 
     /**
     * setcorrectAttempts Method - replace this comment with your own
     * 
     * @param     correctAttempts
     * @return     none
     */
    
    
    public void setcorrectAttempts(int noAtt){
    
    this.incorrectAttempts= noAtt;
    
    };
    
    
     /**
     * gets  number of correct attempts
     */ 
    public int getCorrectAttempts(){
    
    return this.correctAttempts;
    
    };
    
   /**
     * Increments number of correct attempts
     */
    
    public void addCorrectAttempts(){
    
    this.correctAttempts++;
    
    };
    
  
    
    
     /**
     * setincorrectAttempts Method - replace this comment with your own
     * 
     * @param     incorrectAttempts
     * @return     none
     */
      public void setincorrectAttempts(int noAtt){
    
    this.incorrectAttempts= noAtt;
    
    };
    
    
    /**
     * gets  number of incorrect attempts
     */ 
    public int getIncorrectAttempts(){
    
    return this.incorrectAttempts;
    
    };
    
     /**
     * Increments number of incorrect attempts
     */
    
    public void addIncorrectAttempts(){
    
    this.incorrectAttempts++;
    
    };  
    
    
    
    
    
    /**
     * setlocation Method -
     * 
     * @param     location
     * @return     none
     */
    
    
    public void setLocation(int loc){
    
    this.location = loc;
    
    };
    
    
     /**
     * gets  location
     * @param     none
     * @return    location
     */ 
    
    public int getLocation(){
    
    return this.location;
    
    };
    
 
    
        
    /**
     * setEnglishWord Method - replace this comment with your own
     * 
     * @param     englishWord
     * @return     nothing
     */
    
    public void setEnglishWord (String eWord)
    {
    this.englishWord = eWord;
    }; 
    
     /**
     * getEnglishWord Method - replace this comment with your own
     * 
     * @param     englishWord
     * @return     eWord
     */
    
    public String getEnglishWord()
    {
      return this.englishWord ;
    };
  
   /**
     * setforeignWord Method - replace this comment with your own
     * 
     * @param     foreignWord
     * @return     nothing
     */
    
    public void setForeignWord(String fWord)
    {
    this.foreignWord = fWord;
    };
 

 /**
     * getForeignWord Method - replace this comment with your own
     * 
     * @param     englishWord
     * @return     eWord
     */
  
    public String getForeignWord()
     {
      return this.foreignWord ;
     };
     
     /**
      *  adds a category, there is an unlimited number.
      */  
   
     public void addCategory(String category)
    {
        categories.add(category);
    }
 
    
       public Object showCategories(int num)
    {
        if(num < 0) {
            // This is not a valid note number, so do nothing.
            return 1;
        }
        else if(num < numberOfCategories()) {
            // This is a valid note number, so we can print it.
            return categories.get(num);
        }
        else {
            // This is not a valid note number, so do nothing.
            return 1;
        }
     }
    
    
       public int numberOfCategories()
    {
        return categories.size();
    }
    
     
     
     
}   
  
 

[Paul Sturrock]

How do I declare an arrayList and initilise it in a constructor Method

class Foo {
    private ArrayList list;
 
    public Foo() {
         list = new ArrayList();
    }
}

There you go.

I am presuming you have not tried to compile your code yet? It doesn't look like it will compile - I don't see a wordRecord constructor which takes any parameters.
[ October 04, 2005: Message edited by: Paul Sturrock ]

[Seb Mathe]

It does'nt work because your wordRecord class does'nt have a constructor that match :
wordRecord(int correctAttempts, int incorrectAttempts, int location, String englishWord, String foreignWord, ArrayList categories)

Add this constructor to your wordRecord class, do variables affectations here and it will work fine...

Tips :
- rename wordRecord to WordRecord
- no-arg constructor wordRecord() will just have do call this(0,0,..., ) just like you do in Record

[lupercal hill]

Is this more correct. Thanks for you help. Im leaving out the arraylists as I dont know how difficult they will be to save to disk. They are non fixed size but the records must be a fixed size. I dont know the work around yet.

Could you please look at this code and suggest what else i need to change. The final class Create RandomFile wont compile.

Record Class

 
// Record class for the RandomAccessFile programs.
import java.util.ArrayList;
import java.io.*;
public class Record extends WordRecord {
 
  
   public Record()
   {
      this( 0,0,0, "", "");
   }
 
   public Record( int correctAttempts, int incorrectAttempts, int location, String englishWord,
                  String foreignWord /*ArrayList categories */)
   {
      super( correctAttempts, incorrectAttempts, location, englishWord, foreignWord /*categories*/ );
   }
 
   // Read a record from the specified RandomAccessFile
   public void read( RandomAccessFile file ) throws IOException
   {
      setcorrectAttempts( file.readInt() ); 
      setincorrectAttempts( file.readInt() );
      setLocation( file.readInt() );
      setEnglishWord ( padName( file ) );
      setForeignWord( padName( file ) );
     // how do i read an arraylist from a Random file ,
   }
 
   private String padName( RandomAccessFile f )
      throws IOException
   {
      char name[] = new char[ 15 ], temp;
 
      for ( int i = 0; i < name.length; i++ ) {
         temp = f.readChar();
         name[ i ] = temp;
      }     
      
      return new String( name ).replace( '\0', ' ' );
   }
 
   // Write a record to the specified RandomAccessFile
   public void write( RandomAccessFile file ) throws IOException
   {
      file.writeInt( getAccount() );
      file.writeInt( getCorrectAttempts );
      file.writeInt( getIncorrectAttempts );
      
      
      writeName( file, getLocation() );
      writeName( file, getEnglishWord );
      writeName( file, getForeignWord );
  
   }
 
   private void writeName( RandomAccessFile f, String name )
      throws IOException
   {
      StringBuffer buf = null;
 
      if ( name != null ) 
         buf = new StringBuffer( name );
      else 
         buf = new StringBuffer( 15 );
 
      buf.setLength( 15 );
      f.writeChars( buf.toString() );
   }
 
   // NOTE: This method contains a hard coded value for the
   // size of a record of information.
   public static int size() { return 200; }
}
 

WordRecord Class

import java.util.ArrayList;
/**
 * Write a description of class wordObject here.
 * 
 */
public class WordRecord
{
    // instance variables - replace the example below with your own
   
   private  int correctAttempts;
     private int incorrectAttempts;
    private int location;
     private String englishWord;
    private String foreignWord;
    //private ArrayList categories = new ArrayList();
    
    
    /**
     * Constructor for objects of class wordObject
     */
    public WordRecord()
    {
        // initialise instance variables
       
    
    correctAttempts= 0;
    incorrectAttempts= 0;
    location= 0;
    englishWord= "";
    foreignWord= "";
    //categories.add(0);
    }
    
    
        public WordRecord( int corrAtt, int incorAtt,int loc,String engWord, String forWord    )
    {
        // initialise instance variables
       
    
    setcorrectAttempts(corrAtt);
    setincorrectAttempts(incorAtt);
    setLocation(loc);
     setEnglishWord(engWord);
    setForeignWord(forWord);
    //categories.add(0);
    }
    
    
 
     /**
     * setcorrectAttempts Method - replace this comment with your own
     * 
     * @param     correctAttempts
     * @return     none
     */
    
    
    public void setcorrectAttempts(int noAtt){
    
    this.incorrectAttempts= noAtt;
    
    };
    
    
     /**
     * gets  number of correct attempts
     */ 
    public int getCorrectAttempts(){
    
    return this.correctAttempts;
    
    };
    
   /**
     * Increments number of correct attempts
     */
    
    public void addCorrectAttempts(){
    
    this.correctAttempts++;
    
    };
    
  
    
    
     /**
     * setincorrectAttempts Method - replace this comment with your own
     * 
     * @param     incorrectAttempts
     * @return     none
     */
      public void setincorrectAttempts(int noAtt){
    
    this.incorrectAttempts= noAtt;
    
    };
    
    
    /**
     * gets  number of incorrect attempts
     */ 
    public int getIncorrectAttempts(){
    
    return this.incorrectAttempts;
    
    };
    
     /**
     * Increments number of incorrect attempts
     */
    
    public void addIncorrectAttempts(){
    
    this.incorrectAttempts++;
    
    };  
    
    
    
    
    
    /**
     * setlocation Method -
     * 
     * @param     location
     * @return     none
     */
    
    
    public void setLocation(int loc){
    
    this.location = loc;
    
    };
    
    
     /**
     * gets  location
     * @param     none
     * @return    location
     */ 
    
    public int getLocation(){
    
    return this.location;
    
    };
    
 
    
        
    /**
     * setEnglishWord Method - replace this comment with your own
     * 
     * @param     englishWord
     * @return     nothing
     */
    
    public void setEnglishWord (String eWord)
    {
    this.englishWord = eWord;
    }; 
    
     /**
     * getEnglishWord Method - replace this comment with your own
     * 
     * @param     englishWord
     * @return     eWord
     */
    
    public String getEnglishWord()
    {
      return this.englishWord ;
    };
  
   /**
     * setforeignWord Method - replace this comment with your own
     * 
     * @param     foreignWord
     * @return     nothing
     */
    
    public void setForeignWord(String fWord)
    {
    this.foreignWord = fWord;
    };
 

 /**
     * getForeignWord Method - replace this comment with your own
     * 
     * @param     englishWord
     * @return     eWord
     */
  
    public String getForeignWord()
     {
      return this.foreignWord ;
     };
     
     /**
      *  adds a category, there is an unlimited number.
      */  
   
 /*
     
     public void addCategory(String category)
    {
       categories.add(category);
    }
 
    
       public Object showCategories(int num)
    {
        if(num < 0) {
            // This is not a valid note number, so do nothing.
            return 1;
        }
        else if(num < numberOfCategories()) {
            // This is a valid note number, so we can print it.
            return categories.get(num);
        }
        else {
            // This is not a valid note number, so do nothing.
            return 1;
        }
     }
    
    
       public int numberOfCategories()
    {
        return categories.size();
    }
    
**/     
     
     
}   
  
  

Create RandomFile class

 
// This program creates a random access file sequentially
// by writing 100 empty records to disk.
import java.io.*;
import javax.swing.*;
 
public class CreateRandomFile {
   private WordRecord blank;
   private RandomAccessFile file;
 
   public CreateRandomFile()
   {
      blank = new WordRecord();
      openFile();
   }
 
   private void openFile()
   {
      JFileChooser fileChooser = new JFileChooser();
                   fileChooser.setFileSelectionMode(
                              JFileChooser.FILES_ONLY );
      int result = fileChooser.showSaveDialog( null );
   
      // user clicked Cancel button on dialog
      if ( result == JFileChooser.CANCEL_OPTION )
         return;
 
      File fileName = fileChooser.getSelectedFile();
 
      if ( fileName == null || 
           fileName.getName().equals( "" ) )
         JOptionPane.showMessageDialog( null,
            "Invalid File Name",
            "Invalid File Name",
            JOptionPane.ERROR_MESSAGE );
      else {
         // Open the file
         try {           
            file = new RandomAccessFile( fileName, "rw" );
 
            for ( int i = 0; i < 100; i++ )
               blank.write( file );
 
            System.exit( 0 );
         }
         catch ( IOException e ) {
            JOptionPane.showMessageDialog( null,
               "File does not exist",
               "Invalid File Name",
               JOptionPane.ERROR_MESSAGE );
            System.exit( 1 );
         }
      }
   }
 
   public static void main( String args[] )
   {
      new CreateRandomFile();
   }   
}
 

[Seb Mathe]

It seems to be ok...

But look at your WordRecord constructors... You're doing the same things. You can simplify the no-arg constructor.

[lupercal hill]

Thank you. Would I be better doing this in XML rather then using the RandomFile class