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 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 itÂÂimportjava.util.*;ÂÂpublicclassGFG {   Âpublicstaticvoidmain(String[] args)   Â{       Â// Create a HashMap       ÂHashMap<Integer, String>           Âmap =newHashMap<>();       Â// Populate the HashMap       Âmap.put(1,"Geeks");       Âmap.put(2,"ForGeeks");       Âmap.put(3,"GeeksForGeeks");       Â// Get the key to be removed       ÂintkeyToBeRemoved =2;       Â// Print the initial HashMap       ÂSystem.out.println("Original HashMap: "                          Â+ map);       Â// Get the iterator over the HashMap       ÂIterator<Map.Entry<Integer, String> >           Âiterator = map.entrySet().iterator();       Â// Iterate over the HashMap       Âwhile(iterator.hasNext()) {           Â// Get the entry at this iteration           ÂMap.Entry<Integer, String>               Âentry               Â= iterator.next();           Â// Check if this key is the required key           Âif(keyToBeRemoved == entry.getKey()) {               Â// Remove this entry from HashMap               Âiterator.remove();           Â}       Â}       Â// Print the modified HashMap       ÂSystem.out.println("Modified HashMap: "                          Â+ map);   Â}}Output:Original HashMap: {1=Geeks, 2=ForGeeks, 3=GeeksForGeeks} Modified HashMap: {1=Geeks, 3=GeeksForGeeks} - Using Java 8 lambda expressions:
- 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 itÂÂimportjava.util.*;ÂÂpublicclassGFG {   Âpublicstaticvoidmain(String[] args)   Â{       Â// Create a HashMap       ÂHashMap<Integer, String>           Âmap =newHashMap<>();       Â// Populate the HashMap       Âmap.put(1,"Geeks");       Âmap.put(2,"ForGeeks");       Âmap.put(3,"GeeksForGeeks");       Â// Get the key to be removed       ÂintkeyToBeRemoved =2;       Â// Print the initial HashMap       ÂSystem.out.println("Original HashMap: "                          Â+ map);       Â// Remove the specified entry from the Map       Âmap.entrySet()           Â.removeIf(               Âentry -> (keyToBeRemoved == entry.getKey()));       Â// Print the modified HashMap       ÂSystem.out.println("Modified HashMap: "                          Â+ map);   Â}}Output:Original HashMap: {1=Geeks, 2=ForGeeks, 3=GeeksForGeeks} Modified HashMap: {1=Geeks, 3=GeeksForGeeks}
