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Thread: Help Huffman Coding>>

  1. #1
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    Exclamation Help Huffman Coding>>

    Hi
    I need help in the following code
    HuffmanCodeStudent.zip
    there are some missing functions need to complete
    QueueTree
    makeHuffTree
    makeCodeTable
    decode




    note : this is a homework and it's due date is Sunday 24th July
    so any help soon is appreciated .
    thx in advance
    Last edited by cool_97; July 22nd, 2011 at 04:42 AM.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Help Huffman Coding>>

    You need to show the code you have with comments that describe how you are implementing the algorithm and your questions about the problems you are having.

    You better put in a little more effort than this post shows if you want it done so soon.

  3. #3
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    Default Re: Help Huffman Coding>>

    This is Node class
    ----------------

    // huffman.java
    // demonstrates Huffman trees
    // to run this program: C>java HuffmanApp
    import java.io.*;
    import java.util.*;               // for Stack class
    ////////////////////////////////////////////////////////////////
    class Node
       {
       public char ch;                // letter
       public int freq;               // instances of this letter
       public Node leftChild;         // this node's left child
       public Node rightChild;        // this node's right child
    // -------------------------------------------------------------
       Node(char c, int f)            // constructor
          {
          ch = c;
          freq = f;
          }
    // -------------------------------------------------------------
       public void displayNode()      // display ourself
          { System.out.print( ch + "" + freq ); }
       }  // end class Node
    ////////////////////////////////////////////////////////////////
    class Tree
       {
       public Node root;              // first node of tree
    // -------------------------------------------------------------
       public Tree(Node nd)           // constructor
          { root = nd; }              // root of tree from argument
    // -------------------------------------------------------------
       public int getFreq()           // returns node's word freq
          { return root.freq; }
    // -------------------------------------------------------------
       public void display()
          {
          Stack globalStack = new Stack();
          globalStack.push(root);
          int nBlanks = 32;
          boolean isRowEmpty = false;
          System.out.println(
          "......................................................");
          while(isRowEmpty==false)
             {
             Stack localStack = new Stack();
             isRowEmpty = true;
     
             for(int j=0; j<nBlanks; j++)
                System.out.print(' ');
     
             while(globalStack.isEmpty()==false)
                {
                Node temp = (Node)globalStack.pop();
                if(temp != null)
                   {
                   temp.displayNode();
                   localStack.push(temp.leftChild);
                   localStack.push(temp.rightChild);
     
                   if(temp.leftChild != null ||
                                       temp.rightChild != null)
                      isRowEmpty = false;
                   }
                else
                   {
                   System.out.print("--");
                   localStack.push(null);
                   localStack.push(null);
                   }
                for(int j=0; j<nBlanks*2-2; j++)
                   System.out.print(' ');
                }  // end while globalStack not empty
             System.out.println();
             nBlanks /= 2;
             while(localStack.isEmpty()==false)
                globalStack.push( localStack.pop() );
             }  // end while isRowEmpty is false
          System.out.println(
          "......................................................");
          }  // end displayTree()
    // -------------------------------------------------------------
       }  // end class Tree
    ////////////////////////////////////////////////////////////////
    class PriorityQ
       {
       // array in sorted order, from max at 0 to min at size-1
       private int maxSize;
       private Tree[] queArray;
       private int nItems;
    //-------------------------------------------------------------
       public PriorityQ(int s)          // constructor
          {
          maxSize = s;
          queArray = new Tree[maxSize];
          nItems = 0;
          }
    //-------------------------------------------------------------
       public void insert(Tree item)    // insert item
          {
          int j;
     
          if(nItems==0)                         // if no items,
             queArray[nItems++] = item;         // insert at 0
          else                                  // if items,
             {
             for(j=nItems-1; j>=0; j--)      // start at end,
                {                            // if new item larger,
                if( item.root.freq > queArray[j].root.freq )
                   queArray[j+1] = queArray[j]; // shift upward
                else                            // if smaller,
                   break;                       // done shifting
                }  // end for
             queArray[j+1] = item;              // insert it
             nItems++;
             }  // end else (nItems > 0)
          }  // end insert()
    //-------------------------------------------------------------
       public Tree remove()             // remove minimum item
          { return queArray[--nItems]; }
    //-------------------------------------------------------------
       public Tree peekMin()            // peek at minimum item
          { return queArray[nItems-1]; }
    //-------------------------------------------------------------
       public boolean isEmpty()         // true if queue is empty
          { return (nItems==0); }
    //-------------------------------------------------------------
       public boolean isFull()          // true if queue is full
          { return (nItems == maxSize); }
    //-------------------------------------------------------------
       public int getSize()
          { return nItems; }
    //-------------------------------------------------------------
       }  // end class PriorityQ
    ////////////////////////////////////////////////////////////////
    Last edited by cool_97; July 22nd, 2011 at 09:44 AM.

  4. #4
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    Default Re: Help Huffman Coding>>

    here is the class huffman where i need help in the following functions
    private void queueTrees(){
    for each char in the frequancy table loop{
    if freq =0 do nothing
    else
    creat a new node contains the char and the frequency
    creat a tree for the node
    insert node in priority queue
    }

    }

    private void makeHuffTree(){
    loop until one tree in the queue {
    dequeu first node
    deququ second node
    add the frequency of one and two
    creat a new tree with new frequencies as it's root
    connect the new tree in the correct place in the queue
    }
    }
    private void makeCodeTable(Node nd, String bc)
    {
    if the node is not a leaf{
    (external node ) (add symbol like + to make it recognizable, nd.ch=='+')
    call it recursively
    makecodetable (nd.leftchild,bc+"0");

    makecodetable (nd.rightchild,bc+"0");
    }
    else it is aa leaf node so put it in code table
    }
    public void decode()

    -----------------------------------------------------------------------

    import java.io.*;
    import java.util.*;     
    class Huffman
       {
       private PriorityQ theQueue;
       private String inString;        // input from user
       private int strlen;
       private String capsString;      // converted to all caps
       private Tree[] treeArray;
       private Tree huffTree;          // Huffman tree
       private int freqTable[];        // letter frequencies
       private int alphabetSize;       // size of frequency table
       private String codeTable[];     // code for each letter
       private String codedMsg;        // binary string
       private String decodedMsg;      // back to original msg
    // -------------------------------------------------------------
       Huffman(String s)                     // constructor
          {
          inString = s;
          strlen = inString.length();
          alphabetSize = 28;                 // 26 letters, cr, lf
          theQueue = new PriorityQ(alphabetSize); // make the queue
          capsString = "";
          codeTable = new String[alphabetSize];   // make code table
     
          makeFreqTable();          // construct frequency table
          queueTrees();             // put one-node trees in queue
          makeHuffTree();           // construct Huffman tree
          }  // end constructor
    // -------------------------------------------------------------
       public void displayTree()
          {
          if(huffTree != null)
             huffTree.display();
          }
    // -------------------------------------------------------------
      private void makeFreqTable()
          {
          freqTable = new int[alphabetSize];
          int temp;
          char sp = 32;                      // space
          for(int j=0; j<strlen; j++)        // for every char
             {                               // of user's input msg
             char ch = inString.charAt(j);
             if(ch>96 && ch<123)             // lowercase (97-122)
                {
                temp = (int)ch - 32;         // convert to upper
                ch = (char)temp;             //    (65-90)
                }
             if(ch==32)                      // space becomes 91
                ch = 91;
             else if(ch==10)                 // linefeed becomes 92
                ch = 92;
             else if(ch<65 || ch>92)         // if not uppercase
                continue;                    // letter, ignore it
             capsString = capsString + ch;   // add to caps string
             int index = (int)ch - 65;       // convert to 0 to 27
             freqTable[index]++;             // keep count in
             }  // end for                   //    frequency table
          System.out.println(capsString);    // all-caps string
          for(int j=0; j<28; j++)            // row of characters
             System.out.print( (char)(j+65) + " ");
          System.out.println("");
          for(int j=0; j<28; j++)            // row of frequencies
             System.out.print(freqTable[j] + " ");
          System.out.println("");
          }  // end makeFreqTable()
    // -------------------------------------------------------------
       private void queueTrees()             // put trees in queue
          {
    // for each char in frequency table forget unused characters
     
    // make node
     
    // make tree
    // put  the tree in queue
     
          }  // end queueTrees()
    // -------------------------------------------------------------
       private void makeHuffTree()           // make Huffman tree
          {
     
     
          }  // end makeHuffTree()
    // -------------------------------------------------------------
       private void makeCodeTable(Node nd, String bc)
          {
     
          }  // end makeCodeTable()
    // -------------------------------------------------------------
       public void code()                    // encode the msg
          {
          makeCodeTable(huffTree.root, "");
          for(int j=0; j<alphabetSize; j++)  // display code table
             {
             if(codeTable[j] == null)
                continue;
             char ch = (char)(j+65);
             System.out.println(ch + " " + codeTable[j]);
             }
          codedMsg = "";                     // encode the msg
          for(int j=0; j<capsString.length(); j++)   // for each char
             {                                       // get the code
             int index = (int)capsString.charAt(j) - 65;
             codedMsg = codedMsg + codeTable[index]; // add to msg
             }
          System.out.println("Coded message:\n" + codedMsg);
          }  // end code()
    // -------------------------------------------------------------
       public void decode()
          {
          }  // end decode()
    // -------------------------------------------------------------
       }  // end class Huffman
    Last edited by cool_97; July 22nd, 2011 at 09:45 AM.

  5. #5
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    Default Re: Help Huffman Coding>>

    Please edit your code and wrap it in code tags. Use Go Advanced and the # icon.
    This is Node class
    What is your problem with the code you posted? I don't see any questions about your code.

  6. #6
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    Default Re: Help Huffman Coding>>

    main class


    import java.io.*;
    import java.util.*;     
     
    class HuffmanApp
       {
       public static void main(String[] args) throws IOException
          {
          Huffman huff = null;
          int value;
          String str;
     
          while(true)
             {
             System.out.print("Enter first letter of ");
             System.out.print("enter, show, code, or decode: ");
             int choice = getChar();
             switch(choice)
                {
                case 'e':
                   System.out.println(
                      "Enter text lines, terminate with $");
                   str = getText();
                   huff = new Huffman(str);
                   break;
                case 's':
                   huff.displayTree();
                   break;
                case 'c':
                   huff.code();
                   break;
                case 'd':
                   huff.decode();
                   break;
                default:
                   System.out.print("Invalid entry\n");
                }  // end switch
             }  // end while
          }  // end main()
    // -------------------------------------------------------------
       public static String getString() throws IOException
          {
          InputStreamReader isr = new InputStreamReader(System.in);
          BufferedReader br = new BufferedReader(isr);
          String s = br.readLine();
          return s;
          }
    // -------------------------------------------------------------
       public static String getText() throws IOException
          {
          String outStr="", str = "";
          while(true)
             {
             str = getString();
             if( str.equals("$") )
                return outStr;
             outStr = outStr + str + "\n";
             }
          }  // end getText()
    // -------------------------------------------------------------
       public static char getChar() throws IOException
          {
          String s = getString();
          return s.charAt(0);
          }
    //-------------------------------------------------------------
       public static int getInt() throws IOException
          {
          String s = getString();
          return Integer.parseInt(s);
          }
    // -------------------------------------------------------------
       }  // end class HuffmanApp

  7. #7
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    Default Re: Help Huffman Coding>>

    will do
    thx

  8. #8
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    Default Re: Help Huffman Coding>>

    Thanks for using code tags.

    What is your problem with the code you posted? I don't see any questions about your code.

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    Default Re: Help Huffman Coding>>

    actually nothing is wrong put u could see in post # 4
    there 4 empty functions need to fill them up and run the programme

  10. #10
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    Default Re: Help Huffman Coding>>

    Are you thinking that someone here is going to write the code for your "functions"? (methods in java)

  11. #11
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    Default Re: Help Huffman Coding>>

    Quote Originally Posted by Norm View Post
    Are you thinking that someone here is going to write the code for your "functions"? (methods in java)
    7
    hmmmmmmmmmmmmm
    then i'm in the wrong forum

  12. #12
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    Default Re: Help Huffman Coding>>

    i'm in the wrong forum
    Yes, If you expect someone here to write your code for you.

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    Default Re: Help Huffman Coding>>

    Quote Originally Posted by Norm View Post
    Yes, If you expect someone here to write your code for you.
    ok be a dear
    and help me
    in the following code is it correct
    PHP Code:
     private void queueTrees()             // put trees in queue
          
    {
           
    HuffmanApp a = new HuffmanApp();
          for (
    int i =0;i<freqTable.length;i++){
              if (
    freqTable[i]==0)
                  continue;
              else{
                  
    char l codeTable[i].charAt(i);
                  
    Node newNode = new Node (l,freqTable[i]);
                  
                  
    Tree t1 = new Tree(newNode);
                  
    theQueue.insert(t1);
              }
          } 
    PHP Code:
     private void makeHuffTree()           // make Huffman tree
          
    {
           for (
    int i=1;i<alphabetSize;i++){
               
    Tree a=theQueue.remove();
               
    int freq1=a.getFreq();
               
    Tree b =theQueue.remove();
               
    int freq2=b.getFreq();
               
    int newfreq =freq1+freq2;
               
    Node newNode = new Node(' ',newfreq);
               
    Tree c = new Tree(newNode);
               
    theQueue.insert(c);
           }
          

          } 
    PHP Code:
     private void makeCodeTable(Node ndString bc)
          {
           if (
    nd.leftChild!=null && nd.rightChild!=null){
               
    makeCodeTable(nd.leftChild,bc+"0");
               
    makeCodeTable(nd.rightChild,bc+"1");
           }
           else 
               
    codeTable=codeTable+bc;

      }  
    // end makeCodeTable() 
    this one don't know what to do with it
    PHP Code:
      public void decode()
          {
          }  
    // end decode() 

  14. #14
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    Default Re: Help Huffman Coding>>

    the following code is it correct
    Does your program output the correct result?
    If not, please explain what is wrong with the output and show what it needs to look like.

    You've posted bits and pieces of your code, but I'm not sure if it is all here for anyone to compile and execute and test with.

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    Default Re: Help Huffman Coding>>

    Quote Originally Posted by cool_97 View Post
    here is the class huffman where i need help in the following functions
    private void queueTrees(){
    for each char in the frequancy table loop{
    if freq =0 do nothing
    else
    creat a new node contains the char and the frequency
    creat a tree for the node
    insert node in priority queue
    }

    }

    private void makeHuffTree(){
    loop until one tree in the queue {
    dequeu first node
    deququ second node
    add the frequency of one and two
    creat a new tree with new frequencies as it's root
    connect the new tree in the correct place in the queue
    }
    }
    private void makeCodeTable(Node nd, String bc)
    {
    if the node is not a leaf{
    (external node ) (add symbol like + to make it recognizable, nd.ch=='+')
    call it recursively
    makecodetable (nd.leftchild,bc+"0");

    makecodetable (nd.rightchild,bc+"0");
    }
    else it is aa leaf node so put it in code table
    }
    public void decode()

    -----------------------------------------------------------------------

    import java.io.*;
    import java.util.*;     
    class Huffman
       {
       private PriorityQ theQueue;
       private String inString;        // input from user
       private int strlen;
       private String capsString;      // converted to all caps
       private Tree[] treeArray;
       private Tree huffTree;          // Huffman tree
       private int freqTable[];        // letter frequencies
       private int alphabetSize;       // size of frequency table
       private String codeTable[];     // code for each letter
       private String codedMsg;        // binary string
       private String decodedMsg;      // back to original msg
    // -------------------------------------------------------------
       Huffman(String s)                     // constructor
          {
          inString = s;
          strlen = inString.length();
          alphabetSize = 28;                 // 26 letters, cr, lf
          theQueue = new PriorityQ(alphabetSize); // make the queue
          capsString = "";
          codeTable = new String[alphabetSize];   // make code table
     
          makeFreqTable();          // construct frequency table
          queueTrees();             // put one-node trees in queue
          makeHuffTree();           // construct Huffman tree
          }  // end constructor
    // -------------------------------------------------------------
       public void displayTree()
          {
          if(huffTree != null)
             huffTree.display();
          }
    // -------------------------------------------------------------
      private void makeFreqTable()
          {
          freqTable = new int[alphabetSize];
          int temp;
          char sp = 32;                      // space
          for(int j=0; j<strlen; j++)        // for every char
             {                               // of user's input msg
             char ch = inString.charAt(j);
             if(ch>96 && ch<123)             // lowercase (97-122)
                {
                temp = (int)ch - 32;         // convert to upper
                ch = (char)temp;             //    (65-90)
                }
             if(ch==32)                      // space becomes 91
                ch = 91;
             else if(ch==10)                 // linefeed becomes 92
                ch = 92;
             else if(ch<65 || ch>92)         // if not uppercase
                continue;                    // letter, ignore it
             capsString = capsString + ch;   // add to caps string
             int index = (int)ch - 65;       // convert to 0 to 27
             freqTable[index]++;             // keep count in
             }  // end for                   //    frequency table
          System.out.println(capsString);    // all-caps string
          for(int j=0; j<28; j++)            // row of characters
             System.out.print( (char)(j+65) + " ");
          System.out.println("");
          for(int j=0; j<28; j++)            // row of frequencies
             System.out.print(freqTable[j] + " ");
          System.out.println("");
          }  // end makeFreqTable()
    // -------------------------------------------------------------
       private void queueTrees()             // put trees in queue
          {
    // for each char in frequency table forget unused characters
     
    // make node
     
    // make tree
    // put  the tree in queue
     
          }  // end queueTrees()
    // -------------------------------------------------------------
       private void makeHuffTree()           // make Huffman tree
          {
     
     
          }  // end makeHuffTree()
    // -------------------------------------------------------------
       private void makeCodeTable(Node nd, String bc)
          {
     
          }  // end makeCodeTable()
    // -------------------------------------------------------------
       public void code()                    // encode the msg
          {
          makeCodeTable(huffTree.root, "");
          for(int j=0; j<alphabetSize; j++)  // display code table
             {
             if(codeTable[j] == null)
                continue;
             char ch = (char)(j+65);
             System.out.println(ch + " " + codeTable[j]);
             }
          codedMsg = "";                     // encode the msg
          for(int j=0; j<capsString.length(); j++)   // for each char
             {                                       // get the code
             int index = (int)capsString.charAt(j) - 65;
             codedMsg = codedMsg + codeTable[index]; // add to msg
             }
          System.out.println("Coded message:\n" + codedMsg);
          }  // end code()
    // -------------------------------------------------------------
       public void decode()
          {
          }  // end decode()
    // -------------------------------------------------------------
       }  // end class Huffman
    Quote Originally Posted by cool_97 View Post
    This is Node class
    ----------------

    // huffman.java
    // demonstrates Huffman trees
    // to run this program: C>java HuffmanApp
    import java.io.*;
    import java.util.*;               // for Stack class
    ////////////////////////////////////////////////////////////////
    class Node
       {
       public char ch;                // letter
       public int freq;               // instances of this letter
       public Node leftChild;         // this node's left child
       public Node rightChild;        // this node's right child
    // -------------------------------------------------------------
       Node(char c, int f)            // constructor
          {
          ch = c;
          freq = f;
          }
    // -------------------------------------------------------------
       public void displayNode()      // display ourself
          { System.out.print( ch + "" + freq ); }
       }  // end class Node
    ////////////////////////////////////////////////////////////////
    class Tree
       {
       public Node root;              // first node of tree
    // -------------------------------------------------------------
       public Tree(Node nd)           // constructor
          { root = nd; }              // root of tree from argument
    // -------------------------------------------------------------
       public int getFreq()           // returns node's word freq
          { return root.freq; }
    // -------------------------------------------------------------
       public void display()
          {
          Stack globalStack = new Stack();
          globalStack.push(root);
          int nBlanks = 32;
          boolean isRowEmpty = false;
          System.out.println(
          "......................................................");
          while(isRowEmpty==false)
             {
             Stack localStack = new Stack();
             isRowEmpty = true;
     
             for(int j=0; j<nBlanks; j++)
                System.out.print(' ');
     
             while(globalStack.isEmpty()==false)
                {
                Node temp = (Node)globalStack.pop();
                if(temp != null)
                   {
                   temp.displayNode();
                   localStack.push(temp.leftChild);
                   localStack.push(temp.rightChild);
     
                   if(temp.leftChild != null ||
                                       temp.rightChild != null)
                      isRowEmpty = false;
                   }
                else
                   {
                   System.out.print("--");
                   localStack.push(null);
                   localStack.push(null);
                   }
                for(int j=0; j<nBlanks*2-2; j++)
                   System.out.print(' ');
                }  // end while globalStack not empty
             System.out.println();
             nBlanks /= 2;
             while(localStack.isEmpty()==false)
                globalStack.push( localStack.pop() );
             }  // end while isRowEmpty is false
          System.out.println(
          "......................................................");
          }  // end displayTree()
    // -------------------------------------------------------------
       }  // end class Tree
    ////////////////////////////////////////////////////////////////
    class PriorityQ
       {
       // array in sorted order, from max at 0 to min at size-1
       private int maxSize;
       private Tree[] queArray;
       private int nItems;
    //-------------------------------------------------------------
       public PriorityQ(int s)          // constructor
          {
          maxSize = s;
          queArray = new Tree[maxSize];
          nItems = 0;
          }
    //-------------------------------------------------------------
       public void insert(Tree item)    // insert item
          {
          int j;
     
          if(nItems==0)                         // if no items,
             queArray[nItems++] = item;         // insert at 0
          else                                  // if items,
             {
             for(j=nItems-1; j>=0; j--)      // start at end,
                {                            // if new item larger,
                if( item.root.freq > queArray[j].root.freq )
                   queArray[j+1] = queArray[j]; // shift upward
                else                            // if smaller,
                   break;                       // done shifting
                }  // end for
             queArray[j+1] = item;              // insert it
             nItems++;
             }  // end else (nItems > 0)
          }  // end insert()
    //-------------------------------------------------------------
       public Tree remove()             // remove minimum item
          { return queArray[--nItems]; }
    //-------------------------------------------------------------
       public Tree peekMin()            // peek at minimum item
          { return queArray[nItems-1]; }
    //-------------------------------------------------------------
       public boolean isEmpty()         // true if queue is empty
          { return (nItems==0); }
    //-------------------------------------------------------------
       public boolean isFull()          // true if queue is full
          { return (nItems == maxSize); }
    //-------------------------------------------------------------
       public int getSize()
          { return nItems; }
    //-------------------------------------------------------------
       }  // end class PriorityQ
    ////////////////////////////////////////////////////////////////
    Quote Originally Posted by cool_97 View Post
    main class


    import java.io.*;
    import java.util.*;     
     
    class HuffmanApp
       {
       public static void main(String[] args) throws IOException
          {
          Huffman huff = null;
          int value;
          String str;
     
          while(true)
             {
             System.out.print("Enter first letter of ");
             System.out.print("enter, show, code, or decode: ");
             int choice = getChar();
             switch(choice)
                {
                case 'e':
                   System.out.println(
                      "Enter text lines, terminate with $");
                   str = getText();
                   huff = new Huffman(str);
                   break;
                case 's':
                   huff.displayTree();
                   break;
                case 'c':
                   huff.code();
                   break;
                case 'd':
                   huff.decode();
                   break;
                default:
                   System.out.print("Invalid entry\n");
                }  // end switch
             }  // end while
          }  // end main()
    // -------------------------------------------------------------
       public static String getString() throws IOException
          {
          InputStreamReader isr = new InputStreamReader(System.in);
          BufferedReader br = new BufferedReader(isr);
          String s = br.readLine();
          return s;
          }
    // -------------------------------------------------------------
       public static String getText() throws IOException
          {
          String outStr="", str = "";
          while(true)
             {
             str = getString();
             if( str.equals("$") )
                return outStr;
             outStr = outStr + str + "\n";
             }
          }  // end getText()
    // -------------------------------------------------------------
       public static char getChar() throws IOException
          {
          String s = getString();
          return s.charAt(0);
          }
    //-------------------------------------------------------------
       public static int getInt() throws IOException
          {
          String s = getString();
          return Integer.parseInt(s);
          }
    // -------------------------------------------------------------
       }  // end class HuffmanApp
    these are the classes that i have u could compile but 3 out of four functions don't work
    PHP Code:
    Enter first letter of entershowcode, or decodee
    Enter text lines
    terminate with $
    cool
    $
    COOL
    A B C Exception in thread 
    "main" java.lang.NullPointerException
        at Huffman
    .queueTrees(Huffman.java:76)
        
    at Huffman.<init>(Huffman.java:27)
        
    at HuffmanApp.main(HuffmanApp.java:23)
    D E F G H I J K L M N O P Q R S T U V W X Y Z [  
    0 0 1 0 0 0 0 0 0 0 0 1 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 1 
    actually this function was working and it did decode them but after modifying some functions it didn't

  16. #16
    Super Moderator Norm's Avatar
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    Default Re: Help Huffman Coding>>

    java.lang.NullPointerException
    at Huffman.queueTrees(Huffman.java:76)
    For this error, look at line 76 and see what variable can be null. Then back track to see why that variable does not have a valid value.
    If you can't tell which variable is null, add a println before line 76 to print out the values of all the variables.

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    Default Re: Help Huffman Coding>>

    To test your code there needs to be correct input. Here is a technique to make sure that everyone uses the same input. Put the input into a String and use the Scanner class.

       static Scanner scnr = new Scanner("e\ncool\n$\n\n");  // preload the responses
     
    // -------------------------------------------------------------
       public static String getString() { //throws IOException       {
    //      InputStreamReader isr = new InputStreamReader(System.in);
    //      BufferedReader br = new BufferedReader(isr);
    //      String s = br.readLine();
          return scnr.nextLine();  // get the response from the String above
       }

  18. #18
    Super Moderator Norm's Avatar
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    Default Re: Help Huffman Coding>>

    You have too many "magic" numbers in your code in place of self defining literals. That makes it impossible for anyone reading the code to easily understand what it is doing.
    For example:
    char sp = 32;
    vs
    char sp = ' ';

    What does this 65 represent?
    int index = (int)ch - 65; // convert to 0 to 27

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    Default Re: Help Huffman Coding>>

    Ok let me explain
    these three classes were given to us in class to complete the missing functions

    the programme do the following
    take a line of charecters then print them and encode them to 0's and 1's
    after that printing them
    there is a frequency table to check how many times each letter occuer and code table to save them
    it also decode wich convert them from 1's and 0's to the letters
    and that's that

  20. #20
    Super Moderator Norm's Avatar
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    Default Re: Help Huffman Coding>>

    Another comment on the coding style: too many methods are static. There should be a short main and the rest of the code should be in the constructor:
      public static void main(String[] args) {    //<<<<<<<<<<<<<<
           new HuffmanApp();
       }
     
       Huffman huff = null;        //<<<<<<<<<<<<< an instance variable NOTE<<<
     
       //-------------------------
       public HuffmanApp() {

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    Default Re: Help Huffman Coding>>

    The idea of this forum is that you post the code that isn't working and we help you figure out what's wrong with it so you can fix it. We're not generally that interested in writing it for you - neither of us will learn anything useful.

    If you can't post up your effort at writing the code, try explaining which specific parts of the task you don't understand. If you have an algorithm for decoding Huffman Code, post it and explain where you're having difficulty translating it to Java. If you don't have an algorithm, you need to find one (not really a Java problem).

    You need to know how to do the tasks required by those methods before writing any code. If you can't write out a detailed step-by-step sequence in English for each task, focus on that first. Then we can help you translate your steps into Java.

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    Default Re: Help Huffman Coding>>

    plz visit thread # 14 i posted my effort
    and i have already posted the algorithm
    og each function and the purpose of it
    thx

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    Default Re: Help Huffman Coding>>

    Some confusion here. post#14 is my post.
    i posted my effort
    What methods are the ones that you wrote?

    Look at my post #17.
    I need the input for testing the code.
    I want it to come from a String as per #17, not from the keyboard.
    Last edited by Norm; July 23rd, 2011 at 03:38 PM.

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    Default Re: Help Huffman Coding>>

    queueTrees()
    makeHuffTree()
    makeCodeTable
    but not sure if it's correct

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    Default Re: Help Huffman Coding>>

    i meant 13#
    sry

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