Dictionary Methods in Java

Java 8Object Oriented ProgrammingProgramming

Dictionary is an abstract class that represents a key/value storage repository and operates much like Map. Given a key and value, you can store the value in a Dictionary object. Once the value is stored, you can retrieve it by using its key. Thus, like a map, a dictionary can be thought of as a list of key/value pairs.

Following are the methods defined by Dictionary are listed below −

Sr.NoMethod & Description
1Enumeration elements( )
Returns an enumeration of the values contained in the dictionary.
2Object get(Object key)
Returns the object that contains the value associated with the key. If the key is not in the dictionary, a null object is returned.
3boolean isEmpty( )
Returns true if the dictionary is empty, and returns false if it contains at least one key.
4Enumeration keys( )
Returns an enumeration of the keys contained in the dictionary.
5Object put(Object key, Object value)
Inserts a key and its value into the dictionary. Returns null if the key is not already in the dictionary; returns the previous value associated with the key if the key is already in the dictionary.
6Object remove(Object key)
Removes the key and its value. Returns the value associated with the key. If the key is not in the dictionary, a null is returned.
7int size( )
Returns the number of entries in the dictionary.

Following is an example implementing put() and get() method of the Dictionary class −

Example

import java.util.*;
public class Demo {
   public static void main(String[] args) {
      Dictionary dictionary = new Hashtable();
      dictionary.put("20", "John");
      dictionary.put("40", "Tom");
      dictionary.put("60", "Steve");
      dictionary.put("80", "Kevin");
      dictionary.put("100", "Ryan");
      dictionary.put("120", "Tim");
      dictionary.put("140", "Jacob");
      dictionary.put("160", "David");
      System.out.println("Value at key 20 = " + dictionary.get("20"));
      System.out.println("Value at key 40 = " + dictionary.get("40"));
      System.out.println("Value at key 30 = " + dictionary.get("30"));
      System.out.println("Value at key 90 = " + dictionary.get("90"));
   }
}

Output

Value at key 20 = John
Value at key 40 = Tom
Value at key 30 = null
Value at key 90 = null

Let us see another example wherein we are displaying the Dictionary values as well using the elements () method −

Example

import java.util.*;
public class Demo {
   public static void main(String[] args) {
      Dictionary dictionary = new Hashtable();
      dictionary.put("20", "John");
      dictionary.put("40", "Tom");
      dictionary.put("60", "Steve");
      dictionary.put("80", "Kevin");
      dictionary.put("100", "Ryan");
      dictionary.put("120", "Tim");
      dictionary.put("140", "Jacob");
      dictionary.put("160", "David");
      System.out.println("Dictionary Values...");
      for (Enumeration i = dictionary.elements(); i.hasMoreElements();) {
         System.out.println(i.nextElement());
      }
      System.out.println("Value at key 20 = " + dictionary.get("20"));
      System.out.println("Value at key 40 = " + dictionary.get("40"));
      System.out.println("Value at key 30 = " + dictionary.get("30"));
      System.out.println("Value at key 90 = " + dictionary.get("90"));
   }
}

Output

Dictionary Values...
Tom
Jacob
Steve
Ryan
David
John
Kevin
Tim
Value at key 20 = John
Value at key 40 = Tom
Value at key 30 = null
Value at key 90 = null
raja
Published on 24-Sep-2019 07:46:48
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