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Partial Search from Hash Table in Java
Posted on: April 16, 2007 at 12:00 AM

This section illustrates you how to put some string in the Hash Table through the Java program and get these string easily.

Partial Search from Hash Table in Java

This section illustrates you how to put some string in the Hash Table through the Java program and get these string easily. Here, you will see that the given string which is mentioned with the command "java <file name>" in the command line.

Program Description:

In this section, an example is given with the complete code, which provides you to put some string in the Hash Table of Java and get it for searching. This is done by mentioning a string that has to be searched. This program searches these strings, which are started with the given string or character. For example, if you mention the string "h" then the program searches those strings which are started with the given character or string "h" like "hello" etc.

Here is the code of the program:


import java.util.*;



public class PartialSearcher{

  Hashtable hash;

  String[] sortedArray;

  public static void main(String args[]){

  Hashtable<String,Object> h = new Hashtable<String,Object>();

  h.put("hello", new Integer(1));

  h.put("hell", new Integer(2));

  h.put("alpha", new Integer(3));

  h.put("bye", new Integer(4));

  h.put("hello2", new Integer(5));

  h.put("solly", new Integer(6));

  h.put("sally", new Integer(7));

  h.put("silly", new Integer(8));

  h.put("zorro", new Integer(9));

  h.put("hi", new Integer(10));

  PartialSearcher p = new PartialSearcher(h);

  if(args.length == 0){

  System.out.println("Usage: Search string missing.");

  return;

  }

  else{

  Object[] objs = p.match(args[0]);

  for(int i = 0; i < objs.length; i++)

  System.out.println(objs[i]);

  }

  }

  

  public PartialSearcher(Hashtable h){

  hash = h;

  createSortedArray();

  }

  

  public Object[] match(String s){

  int startIdx = 

  binarySearch(sortedArray, s, 0, sortedArray.length-1);

  int endIdx = 

	binarySearch(sortedArray, s+ '\uFFFF', 0, sortedArray.length-1);

  Object[] objs = new Object[endIdx-startIdx];

  for (int i = startIdx ; i < endIdx; i++)

  objs[i-startIdx] = sortedArray[i];

  return objs;

  }

  

  public void createSortedArray(){

  sortedArray = new String[hash.size()];

  Enumeration e = hash.keys();

  for(int i = 0; e.hasMoreElements(); i++)

  sortedArray[i] = (String)e.nextElement();

  quicksort(sortedArray, 0, sortedArray.length-1);

  }



  public static int binarySearch(String[] arr, 

  String elem, int fromIndex, int toIndex){

  int mid,cmp;

  while (fromIndex <= toIndex){

  mid =(fromIndex + toIndex)/2;

  if((cmp = arr[mid].compareTo(elem)) < 0)

  fromIndex = mid + 1;

  else if(cmp > 0)

  toIndex = mid - 1;

  else

  return mid;

  }

  return fromIndex;

  }



  public void quicksort(String[] arr, int lo, int hi){

  if(lo >= hi)

  return;

  int mid = (lo + hi) / 2;

  String tmp;

  String middle = arr[mid];

  if(arr[lo].compareTo(middle) > 0){

  arr[mid] = arr[lo];

  arr[lo] = middle;

  middle = arr[mid];

  }

  if(middle.compareTo(arr[hi]) > 0){

  arr[mid] = arr[hi];

  arr[hi] = middle;

  middle = arr[mid];

  if(arr[lo].compareTo(middle) > 0){

  arr[mid] = arr[lo];

  arr[lo] = middle;

  middle = arr[mid];

  }

  }

  int left = lo + 1;

  int right = hi - 1;

  if(left >= right)

  return;

  for( ;; ){

  while(arr[right].compareTo(middle ) > 0){

  right--;

  }

  while(left < right && arr[left].compareTo(middle) <= 0){

  left++;

  }

  if(left < right){

  tmp = arr[left];

  arr[left] = arr[right];

  arr[right] = tmp;

  right--;

  }

  else{

  break;

  }

  }

  quicksort(arr, lo, left);

  quicksort(arr, left + 1, hi);

  }

}

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