Java Hashtable remove() Method

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Description

The Java Hashtable remove(Object key) method is used to remove the key (and its corresponding value) from this hashtable.

Declaration

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

public V remove(Object key)

Parameters

key − This is the key that needs to be removed.

Return Value

The method call returns the value to which the key had been mapped in this hashtable, or null if the key did not have a mapping.

Exception

NullPointerException − This is thrown if the specified key is null.

Removing an Entry from a HashTable of Integer, Integer Pair Example

The following example shows the usage of Java Hashtable remove() method to remove an entry from a Hashtable. We've created a Hashtable object of Integer,Integer pairs. Then few entries are added, table is printed. Using remove() method, an entry is removed from the table and table is printed again.

package com.tutorialspoint;

import java.util.Hashtable;

public class HashtableDemo {
   public static void main(String args[]) {
      
      // create hash table
      Hashtable<Integer,Integer> hashtable = new Hashtable<>();

      // populate hash table
      hashtable.put(1, 1);
      hashtable.put(2, 3);
      hashtable.put(3, 3); 

      System.out.println("Initial table elements: " + hashtable);

      // remove one entry
      hashtable.remove(2);

      System.out.println("Hashtable elements after removing an entry: " + hashtable);
   }    
}

Output

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

Initial table elements: {3=3, 2=3, 1=1}
Hashtable elements after removing an entry: {3=3, 1=1}

Removing an Entry from a HashTable of Integer, String Pair Example

The following example shows the usage of Java Hashtable remove() method to remove an entry from a Hashtable. We've created a Hashtable object of Integer,String pairs. Then few entries are added, table is printed. Using remove() method, an entry is removed from the table and table is printed again.

package com.tutorialspoint;

import java.util.Hashtable;

public class HashtableDemo {
   public static void main(String args[]) {
      
      // create hash table
      Hashtable<Integer,String> hashtable = new Hashtable<>();

      // populate hash table
      hashtable.put(1, "tutorials");
      hashtable.put(2, "point");
      hashtable.put(3, "is best"); 

      System.out.println("Initial table elements: " + hashtable);

      // remove one entry
      hashtable.remove(2);

      System.out.println("Hashtable elements after removing an entry: " + hashtable);
   }    
}

Output

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

Initial table elements: {3=is best, 2=point, 1=tutorials}
Hashtable elements after removing an entry: {3=is best, 1=tutorials}

Removing an Entry from a HashTable of Integer, Object Pair Example

The following example shows the usage of Java Hashtable remove() method to remove an entry from a Hashtable. We've created a Hashtable object of Integer,Student pairs. Then few entries are added, table is printed. Using remove() method, an entry is removed from the table and table is printed again.

package com.tutorialspoint;

import java.util.Hashtable;

public class HashtableDemo {
   public static void main(String args[]) {
      
      // create hash table
      Hashtable<Integer,Student> hashtable = new Hashtable<>();

      // populate hash table
      hashtable.put(1, new Student(1, "Julie"));
      hashtable.put(2, new Student(2, "Robert"));
      hashtable.put(3, new Student(3, "Adam"));

      System.out.println("Initial table elements: " + hashtable);

      // remove one entry
      hashtable.remove(2);

      System.out.println("Hashtable elements after removing an entry: " + hashtable);
   }    
}
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.

Initial table elements: {3=[ 3, Adam ], 2=[ 2, Robert ], 1=[ 1, Julie ]}
Hashtable elements after removing an entry: {3=[ 3, Adam ], 1=[ 1, Julie ]}