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Dictionary Methods in Java
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.No | Method & Description |
|---|---|
| 1 | Enumeration elements( ) Returns an enumeration of the values contained in the dictionary. |
| 2 | Object 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. |
| 3 | boolean isEmpty( ) Returns true if the dictionary is empty, and returns false if it contains at least one key. |
| 4 | Enumeration keys( ) Returns an enumeration of the keys contained in the dictionary. |
| 5 | Object 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. |
| 6 | Object 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. |
| 7 | int 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
Updated on: 24-Sep-2019
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