Java HashMap remove() Method

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Description

The Java HashMap remove() method is used to remove the mapping for the specified key from this map if present.

Declaration

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

public V remove(Object key)

Parameters

key − This is the key whose mapping is to be removed from the map.

Return Value

The method call returns the previous value associated with key, or null if there was no mapping for key.

Exception

NA

Removing a key,value pair from a HashMap of Integer, Integer Pair Example

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

package com.tutorialspoint;

import java.util.HashMap;

public class HashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      HashMap<Integer,Integer> newmap = new HashMap<>();

      // populate hash map
      newmap.put(1, 1);
      newmap.put(2, 3);
      newmap.put(3, 3); 

      System.out.println("Initial map elements: " + newmap);

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

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

Output

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

Initial map elements: {1=1, 2=3, 3=3}
Map elements after removing an entry: {1=1, 3=3}

Removing a key,value pair from a HashMap of Integer, String Pair Example

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

package com.tutorialspoint;

import java.util.HashMap;

public class HashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      HashMap<Integer,String> newmap = new HashMap<>();

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

      System.out.println("Initial map elements: " + newmap);

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

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

Output

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

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

Removing a key,value pair from a HashMap of Integer, Student Pair Example

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

package com.tutorialspoint;

import java.util.HashMap;

public class HashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      HashMap<Integer,Student> newmap = new HashMap<>();

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

      System.out.println("Initial map elements: " + newmap);

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

      System.out.println("Map elements after removing an entry: " + newmap);
   }
}
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 map elements: {1=[ 1, Julie ], 2=[ 2, Robert ], 3=[ 3, Adam ]}
Map elements after removing an entry: {1=[ 1, Julie ], 3=[ 3, Adam ]}