Remove an Entry using key from HashMap while Iterating over it

11 Dec, 2018
Given a HashMap and a key in Java, the task is to remove an entry from this HashMap using the key, while iterating over it.
Examples:
Input: HashMap: {1=Geeks, 2=ForGeeks, 3=GeeksForGeeks}, key = 2
Output: {1=Geeks, 3=GeeksForGeeks}

Input: HashMap: {1=G, 2=e, 3=e, 4=k, 5=s}, key = 3
Output: {1=G, 2=e, 4=k, 5=s}

Using Java 7 and before:Get the HashMap and the KeyCreate an iterator to iterate over the HashMap using HashMap.iterate() method.Iterate over the HashMap using the Iterator.hasNext() method.While iterating, check for the key at that iteration to be equal to the key specified. The entry key of the Map can be obtained with the help of entry.getKey() method.If the key matches, remove the entry of that iteration from the HashMap using remove() method.The required entry has been successfully removed.Program:// Java program to remove an entry using key// from a HashMap while iterating over it  import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Create a HashMap        HashMap<Integer, String>            map = new HashMap<>();          // Populate the HashMap        map.put(1, "Geeks");        map.put(2, "ForGeeks");        map.put(3, "GeeksForGeeks");          // Get the key to be removed        int keyToBeRemoved = 2;          // Print the initial HashMap        System.out.println("Original HashMap: "                           + map);          // Get the iterator over the HashMap        Iterator<Map.Entry<Integer, String> >            iterator = map.entrySet().iterator();          // Iterate over the HashMap        while (iterator.hasNext()) {              // Get the entry at this iteration            Map.Entry<Integer, String>                entry                = iterator.next();              // Check if this key is the required key            if (keyToBeRemoved == entry.getKey()) {                  // Remove this entry from HashMap                iterator.remove();            }        }          // Print the modified HashMap        System.out.println("Modified HashMap: "                           + map);    }}Output:Original HashMap: {1=Geeks, 2=ForGeeks, 3=GeeksForGeeks}
Modified HashMap: {1=Geeks, 3=GeeksForGeeks}

Get the HashMap and the KeyCreate an iterator to iterate over the HashMap using HashMap.iterate() method.Iterate over the HashMap using the Iterator.hasNext() method.While iterating, check for the key at that iteration to be equal to the key specified. The entry key of the Map can be obtained with the help of entry.getKey() method.If the key matches, remove the entry of that iteration from the HashMap using remove() method.The required entry has been successfully removed.
Get the HashMap and the Key
Create an iterator to iterate over the HashMap using HashMap.iterate() method.
Iterate over the HashMap using the Iterator.hasNext() method.
While iterating, check for the key at that iteration to be equal to the key specified. The entry key of the Map can be obtained with the help of entry.getKey() method.
If the key matches, remove the entry of that iteration from the HashMap using remove() method.
The required entry has been successfully removed.
Program:
// Java program to remove an entry using key// from a HashMap while iterating over it  import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Create a HashMap        HashMap<Integer, String>            map = new HashMap<>();          // Populate the HashMap        map.put(1, "Geeks");        map.put(2, "ForGeeks");        map.put(3, "GeeksForGeeks");          // Get the key to be removed        int keyToBeRemoved = 2;          // Print the initial HashMap        System.out.println("Original HashMap: "                           + map);          // Get the iterator over the HashMap        Iterator<Map.Entry<Integer, String> >            iterator = map.entrySet().iterator();          // Iterate over the HashMap        while (iterator.hasNext()) {              // Get the entry at this iteration            Map.Entry<Integer, String>                entry                = iterator.next();              // Check if this key is the required key            if (keyToBeRemoved == entry.getKey()) {                  // Remove this entry from HashMap                iterator.remove();            }        }          // Print the modified HashMap        System.out.println("Modified HashMap: "                           + map);    }}
Original HashMap: {1=Geeks, 2=ForGeeks, 3=GeeksForGeeks}
Modified HashMap: {1=Geeks, 3=GeeksForGeeks}

Using Java 8 lambda expressions:Get the HashMap and the KeyGet the entry set of this map using HashMap.entrySet() method.Using lambda expression, remove the entry from the map if the key is equal to the key specified. The entry key of the Map can be obtained with the help of entry.getKey() method.The required entry has been successfully removed.Program:// Java program to remove an entry using key// from a HashMap while iterating over it  import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Create a HashMap        HashMap<Integer, String>            map = new HashMap<>();          // Populate the HashMap        map.put(1, "Geeks");        map.put(2, "ForGeeks");        map.put(3, "GeeksForGeeks");          // Get the key to be removed        int keyToBeRemoved = 2;          // Print the initial HashMap        System.out.println("Original HashMap: "                           + map);          // Remove the specified entry from the Map        map.entrySet()            .removeIf(                entry -> (keyToBeRemoved == entry.getKey()));          // Print the modified HashMap        System.out.println("Modified HashMap: "                           + map);    }}Output:Original HashMap: {1=Geeks, 2=ForGeeks, 3=GeeksForGeeks}
Modified HashMap: {1=Geeks, 3=GeeksForGeeks}

Get the HashMap and the KeyGet the entry set of this map using HashMap.entrySet() method.Using lambda expression, remove the entry from the map if the key is equal to the key specified. The entry key of the Map can be obtained with the help of entry.getKey() method.The required entry has been successfully removed.
Get the HashMap and the Key
Get the entry set of this map using HashMap.entrySet() method.
Using lambda expression, remove the entry from the map if the key is equal to the key specified. The entry key of the Map can be obtained with the help of entry.getKey() method.
The required entry has been successfully removed.
Program:
// Java program to remove an entry using key// from a HashMap while iterating over it  import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Create a HashMap        HashMap<Integer, String>            map = new HashMap<>();          // Populate the HashMap        map.put(1, "Geeks");        map.put(2, "ForGeeks");        map.put(3, "GeeksForGeeks");          // Get the key to be removed        int keyToBeRemoved = 2;          // Print the initial HashMap        System.out.println("Original HashMap: "                           + map);          // Remove the specified entry from the Map        map.entrySet()            .removeIf(                entry -> (keyToBeRemoved == entry.getKey()));          // Print the modified HashMap        System.out.println("Modified HashMap: "                           + map);    }}
Original HashMap: {1=Geeks, 2=ForGeeks, 3=GeeksForGeeks}
Modified HashMap: {1=Geeks, 3=GeeksForGeeks}

Java - util package
Java-Collections
Java-HashMap
Java-Map-Programs
Java
Java
Java-Collections
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.