Java Dictionary remove() Method

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Description

The Java Dictionary remove(Object key) method removes the value and it's corresponding key from this dictionary.

Declaration

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

public abstract V remove(Object key)

Parameters

key − the key to be removed.

Return Value

This method returns the value to which the key had been mapped, or null if the key did not have a mapping.

Exception

NullPointerException − if key is null.

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

The following example shows the usage of Java Dictionary remove(Object) method. We're creating a dictionary instance using Hashtable object of Integer, Integer pairs. Then we've added few elements to it. Then a element is removed using remove(Object) 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 3 elements
      dictionary.put(1, 1);
      dictionary.put(2, 2);
      dictionary.put(3, 3);

      // remove one element
      dictionary.remove(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 −

3
1

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

The following example shows the usage of Java Dictionary remove(Object) method. We're creating a dictionary instance using Hashtable object of Integer, String pairs. Then we've added few elements to it. Then a element is removed using remove(Object) 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");
      dictionary.put(3, "Three");

      // remove one element
      dictionary.remove(2);
      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 −

Three
One

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

The following example shows the usage of Java Dictionary remove(Object) method. We're creating a dictionary instance using Hashtable object of Integer, Student pairs. Then we've added few elements to it. Then a element is removed using remove(Object) 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"));
      dictionary.put(3, new Student(3, "Adam"));

      // remove one element
      dictionary.remove(2);
      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 −

[ 3, Adam ]
[ 1, Julie ]