Java Dictionary put() Method

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Description

The Java Dictionary put(K key,V value) method maps the specified key to the specified value in this dictionary.

Declaration

Following is the declaration for java.util.Dictionary.keys() method

public abstract V put(K key,V value)

Parameters

• key − the hashtable key.

• value − the value.

Return Value

This method returns the value to which the key was mapped in this dictionary, or null if the key did not have a mapping.

Exception

NullPointerException − if the value or key is null

Adding a Mapping of Key-Value to Dictionary of Integer,Integer Pair Example

The following example shows the usage of Java Dictionary put(K,V) method. We're creating a dictionary instance using Hashtable object of Integer, Integer pairs. Then we've added few elements to it using put(K,V) method. An enumeration is retrieved using elements() method and enumeration is then iterated to print the elements of the dictionary.

package com.tutorialspoint;

import java.util.Enumeration;
import java.util.Dictionary;
import java.util.Hashtable;

public class DictionaryDemo {
   public static void main(String[] args) {

      // create a new hashtable
      Dictionary<Integer, Integer> dictionary = new Hashtable<>();

      // add 2 elements
      dictionary.put(1, 1);
      dictionary.put(2, 2);

      Enumeration<Integer> enumeration = dictionary.elements();

      while(enumeration.hasMoreElements()) {
         System.out.println(enumeration.nextElement());
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

2
1

Adding a Mapping of Key-Value to Dictionary of Integer,String Pair Example

The following example shows the usage of Java Dictionary put(K,V) method. We're creating a dictionary instance using Hashtable object of Integer, String pairs. Then we've added few elements to it using put(K,V) method. An enumeration is retrieved using elements() method and enumeration is then iterated to print the elements of the dictionary.

package com.tutorialspoint;

import java.util.Enumeration;
import java.util.Dictionary;
import java.util.Hashtable;

public class DictionaryDemo {
   public static void main(String[] args) {

      // create a new hashtable
      Dictionary<Integer, String> dictionary = new Hashtable<>();

      // add 2 elements
      dictionary.put(1, "One");
      dictionary.put(2, "Two");

      Enumeration<String> enumeration = dictionary.elements();

      while(enumeration.hasMoreElements()) {
         System.out.println(enumeration.nextElement());
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Two
One

Adding a Mapping of Key-Value to Dictionary of Integer,Object Pair Example

The following example shows the usage of Java Dictionary put(K,V) method. We're creating a dictionary instance using Hashtable object of Integer, Student pairs. Then we've added few elements to it using put(K,V) method. An enumeration is retrieved using elements() method and enumeration is then iterated to print the elements of the dictionary.

package com.tutorialspoint;

import java.util.Enumeration;
import java.util.Dictionary;
import java.util.Hashtable;

public class DictionaryDemo {
   public static void main(String[] args) {

      // create a new hashtable
      Dictionary<Integer, Student> dictionary = new Hashtable<>();

      // add 2 elements
      dictionary.put(1, new Student(1, "Julie"));
      dictionary.put(2, new Student(2, "Robert"));

      Enumeration<Student> enumeration = dictionary.elements();

      while(enumeration.hasMoreElements()) {
         System.out.println(enumeration.nextElement());
      }
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result −

[ 2, Robert ]
[ 1, Julie ]