public void displayEachCharOnce( String str )
{
    String noRepeat = new String();
    for( int i = 0; i < str.length(); i++ )
    {
        // get the next character in string str
        char c = str.charAt( i );
        // check to see if character is in noRepeat string
        if( noRepeat.indexOf( c ) == -1 )
        {
            // character is not in noRepeat 
            // so add it to the end of noRepeat string
            noRepeat = noRepeat.concat( String.valueOf( c ) );          
        }
    }
    // print out the string with no repeating characters
    System.out.println( noRepeat );
}

import java.util.Enumeration;
import java.util.Hashtable;
 
public class CountChar
{
  public void countEachChar( String str )
  {
    Hashtable hashtable = new Hashtable();
    for( int i = 0; i < str.length(); i++ )
    {
      // get the next character in the string
      Character c = new Character( str.charAt( i ) );
      // check to see if the character is in the hashtable
      if( hashtable.contains( c ) )
      {
        // get the related character occurrence count
        Integer i = (Integer) hashtable.get( c );
        // increment the character count
        i = new Integer( i.intValue() + 1 );
        // put the character count back into the hashtable
        hashtable.put( c, i );
      }
      else
      {
        // add the character to the hashtable
        hashtable.put( c, new Integer( 0 ) );
      }
    }
 
    // print out the characters and the no of occurrences
    Enumeration enum = hashtable.keys();
    while( enum.hasNext() )
    {
       // get the next key
       Character c = (Character) enum.next();
       // get the related value
       Integer i = (Integer) enum.get( c );
 
       // print to display
       System.out.println( c + " : " + i );
    }
  }
}