This Java tip illustrates a method of creating a Hash Table. Hash table is generally used in searching applications. Hash table increases the search efficiency by creating a key corresponding to the values in the table.

 // Create a hash table
    Map map = new HashMap();    
    map = new TreeMap();        // sorted map
    // Add key/value pairs to the map
    map.put("x", new Integer(1));
    map.put("y", new Integer(2));
    map.put("z", new Integer(3));
    // Get number of entries in map
    int size = map.size();        // 2
    // Adding an entry whose key exists in the map causes
    // the new value to replace the old value
    Object oldValue = map.put("x", new Integer(9));  // 1
    // Remove an entry from the map and 
    // return the value of the removed entry
    oldValue = map.remove("c");  // 3
    // Iterate over all keys in the table 
    Iterator it = map.keySet().iterator();
    while (it.hasNext()) {
        // Retrieve key
        Object key =;
    // Iterate over all values in table 
    it = map.values().iterator();
    while (it.hasNext()) {
        // Get value
        Object value =;