Remove an Entry using value from HashMap while Iterating over it
Given a HashMap and a value in Java, the task is to remove an entry from this HashMap using the value, while iterating over it.
Examples:
Input: HashMap: {1=Beginner, 2=ForBeginner, 3=w3wiki}, value = “ForBeginner”
Output: {1=Beginner, 3=w3wiki}Input: HashMap: {1=G, 2=e, 3=e, 4=k, 5=s}, value = k
Output: {1=G, 2=e, 3=e, 5=s}
- Using Java 7 and before:
- Get the HashMap and the Value
- 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 value at that iteration to be equal to the value specified. The entry value of the Map can be obtained with the help of entry.getValue() method.
- If the value matches, remove the entry of that iteration from the HashMap using remove() method.
- The required entry has been successfully removed.
Syntax:
Iterator
> iterator = map.entrySet().iterator(); while (iterator.hasNext()) { Map.Entry entry = iterator.next(); if (valueToBeRemoved.equals(entry.getValue())) { iterator.remove(); } } Below is the implementation of the above approach:
// Java program to remove an entry using value
// 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
,
"Beginner"
);
map.put(
2
,
"ForBeginner"
);
map.put(
3
,
"w3wiki"
);
// Get the value to be removed
String valueToBeRemoved =
"ForBeginner"
;
// 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 value is the required value
if
(valueToBeRemoved.equals(entry.getValue())) {
// Remove this entry from HashMap
iterator.remove();
}
}
// Print the modified HashMap
System.out.println(
"Modified HashMap: "
+ map);
}
}
Output:Original HashMap: {1=Beginner, 2=ForBeginner, 3=w3wiki} Modified HashMap: {1=Beginner, 3=w3wiki}
- Using Java 8 lambda expressions:
- Get the HashMap and the Value
- Get the entry set of this map using HashMap.entrySet() method.
- Using lambda expression, remove the entry from the map if the value is equal to the value specified. The entry value of the Map can be obtained with the help of entry.getValue() method.
- The required entry has been successfully removed.
Syntax:
map.entrySet() .removeIf( entry -> (valueToBeRemoved .equals(entry.getValue())));
Below is the implementation of the above approach:
// Java program to remove an entry using value
// 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
,
"Beginner"
);
map.put(
2
,
"ForBeginner"
);
map.put(
3
,
"w3wiki"
);
// Get the value to be removed
String valueToBeRemoved =
"ForBeginner"
;
// Print the initial HashMap
System.out.println(
"Original HashMap: "
+ map);
// Remove the specified entry from the Map
map.entrySet()
.removeIf(
entry -> (valueToBeRemoved.equals(entry.getValue())));
// Print the modified HashMap
System.out.println(
"Modified HashMap: "
+ map);
}
}
Output:Original HashMap: {1=Beginner, 2=ForBeginner, 3=w3wiki} Modified HashMap: {1=Beginner, 3=w3wiki}
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