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Frequency String function help

1 reply on 1 page. Most recent reply: May 30, 2003 5:24 AM by Rahul

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Posts: 83
Nickname: onorok
Registered: May, 2002

Frequency String function help Posted: May 30, 2003 3:32 AM
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This is supposed to go through a String and find the frequency of all the characters in the String, and create a table with the data found.
I am getting out of bounds errors in the getFreq().
Someone else look at this please.

import java.util.StringTokenizer;
public class HuffmanTree
	//Some class variables.
	char[][] freqTable;
	int row=0, col=0;
	public HuffmanTree(String sentence){
		freqTable=new char[2][sentence.length()];//2d-array same size as the string arg.
		getFreq(sentence, 0);
	 Name: getFreq()
	 Parameters: String, int
	 Declared variables:char current, bool doIt, int freqCount
	 	char fc.
	 Return value: void
	 Algorithm: (assumes the user puts all the characters in the same case)
	 	getFreq(entireString, starting indx 'initialy at 0')
	 	remove white spaces if flag alows.
	 	frequent count=0
	 	current=char @ stIndx
	 	put current in the 2d-frequency array
	 	for(compare every char in the entire string to char @ stIndx)
	 		every true comparison to the char @ stIndx  add one to a 
	 		counter for that char.
	 	end for. 
	 	remove every instance of the current char.
	 	convert counter int to a char.
	 		put number(counter) in the 2d-frequency array.
	 		++row to drop the place down one.
	 	if(startIndx is not at the end of the string)				
	public void getFreq(String s, int stIndx){
		char current;
		boolean doIt=false;
		if(doIt){//If doneBefore equals false.
			int freqCount=0;
			for(int i=0; i<=s.length(); ++i){
			s=removeChar(s,current);//Removes every instance of the current char from sentence.
			doIt=false;//Remove all the white spaces again.
			char fc=(char)freqCount;
			//Adds the frequency to the same row one column over.
			++row;//Drops down a row, ready for the next one.
		if(stIndx<=s.length())//If not at the end
			getFreq(s, ++stIndx);//recurse.
	 Name: printFreqTable()
	 Parameters: none.
	 Declared variables: none except the for loop counters
	 Return value: void
	 Purpose: To move through the entire Frequency table and 
	 	output it to the screen.
	 Recursive approach algorithm: 
	 	printFreqTable(int startRowIndx, int startColIndx)
	 		print row and column
	 		if col<=col.length
	 			recurse(++startRow, ++startCol)
	public void printFreqTable(){
		System.out.println("Frequency Table:");
		for(int r=0; r<=freqTable[row].length; ++r){//Print the row.
			System.out.println(freqTable[r]+" = ");
			for(int c=0; c<=freqTable[col].length; ++c){//Print the column.
	public String removeWhiteSpaces(String s){
		StringTokenizer sToken=new StringTokenizer(s," ",false);
		StringBuffer sbuff=new StringBuffer();
		s=sbuff.toString();//Converts the StringBuffer sbuff into a regular String.
		return s;
	//Removes at a specific indx.
	public static String removeCharAt(String s, int pos) {
   			return s.substring(0,pos)+s.substring(pos+1);
	//Removes all related characters.
   	public static String removeChar(String s, char c) {
   		String r = "";
   		for (int i = 0; i < s.length(); i ++) {
      		if (s.charAt(i) != c) r += s.charAt(i);
   		return r;
	//The treeNode innner class.
	public class treeNode
		int frequency;
		char value;
		char code='0';
		boolean isRoot;
		public treeNode(int freq, char val, boolean isR)
			this.isRoot=isR;//Set this flag to true if node is root of tree.
	//The treeLeaf inner class.
	public class treeLeaf
		int frequency;
		char value;
		char code='1';
		public treeLeaf(int freq, char val)
	public static void main(String[] args){
		HuffmanTree tree=new HuffmanTree("susie says come over");



Posts: 52
Nickname: wildhorse
Registered: Oct, 2002

Re: Frequency String function help Posted: May 30, 2003 5:24 AM
Reply to this message Reply
Jake, i did find some errors in the code. but debugging is a here's what you want (it follows your format so should be easy to understand):

import java.util.*;
class CharFreq 
    Hashtable ht = new Hashtable();
    CharFreq(String s){
	while (s.length()!=0)
	        int count = 0;
		char c = s.charAt(0);
		for (int i=0; i< s.length() ;i++ )
		        if (c==s.charAt(i))
		ht.put(""+c,new Integer(count));
		s = removeChar(s,c);
	public String removeChar(String s, char c){
	   for (int i=0; i< s.length() ;i++ ){
		if (i==s.indexOf(c)){
		if (i==0){
			s = s.substring(i+1,s.length());
			s = s.substring(0,i) + s.substring(i+1,s.length());
	return s;
	public void display(Hashtable ht){
		Set st = ht.keySet();
		Iterator i = st.iterator();
		String temp="";
		while (i.hasNext())
			temp = (String);
			System.out.println(temp+" = "+ (Integer)ht.get(temp));
	public static void main(String[] args) 
		CharFreq cf = new CharFreq("susie says come over");

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