How to Remove Key-Value Pairs from a Map Based on Values in Java

How to Remove Key-Value Pairs from a Map Based on Values in Java ?

Answer

To remove key-value pairs from a map in Java based on values, you need to iterate through the map and check each value. If the value matches the specified condition, remove the corresponding key-value pair.

✐ Examples

1 Removing Key-Value Pairs with Specific Value

We can remove key-value pairs from a map in Java by iterating through the map and removing pairs with a specific value.

For example,

We start by importing the java.util.HashMap and java.util.Iterator packages, which provide the HashMap class needed to create and manipulate the map and the Iterator class for iterating through the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We create an iterator for the entry set of the map using the iterator() method.
We iterate through the map using a while loop. For each key-value pair, we check if the value matches the specified value 'two'.
If the value matches, we use the remove() method of the iterator to remove the key-value pair from the map.
We print the contents of the map to the console using a for loop and System.out.println to verify that the key-value pairs have been removed.

Java Program

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");
        myMap.put(4, "two");

        // Remove key-value pairs with specific value
        Iterator<Map.Entry<Integer, String>> iterator = myMap.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, String> entry = iterator.next();
            if (entry.getValue().equals("two")) {
                iterator.remove();
            }
        }

        // Print the contents of the map
        for (Map.Entry<Integer, String> entry : myMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

1: one
3: three

2 Removing Key-Value Pairs with a Range of Values

We can remove key-value pairs from a map in Java by iterating through the map and removing pairs with values within a specified range.

For example,

We start by importing the java.util.HashMap and java.util.Iterator packages, which provide the HashMap class needed to create and manipulate the map and the Iterator class for iterating through the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and integer values.
We create an iterator for the entry set of the map using the iterator() method.
We iterate through the map using a while loop. For each key-value pair, we check if the value falls within the specified range (e.g., between 2 and 3 inclusive).
If the value falls within the range, we use the remove() method of the iterator to remove the key-value pair from the map.
We print the contents of the map to the console using a for loop and System.out.println to verify that the key-value pairs have been removed.

Java Program

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, Integer> myMap = new HashMap<>();
        myMap.put(1, 1);
        myMap.put(2, 2);
        myMap.put(3, 3);
        myMap.put(4, 2);

        // Remove key-value pairs with values in the range [2, 3]
        Iterator<Map.Entry<Integer, Integer>> iterator = myMap.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, Integer> entry = iterator.next();
            if (entry.getValue() >= 2 && entry.getValue() <= 3) {
                iterator.remove();
            }
        }

        // Print the contents of the map
        for (Map.Entry<Integer, Integer> entry : myMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

1: 1

3 Removing Key-Value Pairs with Condition-Based Values

We can remove key-value pairs from a map in Java by iterating through the map and removing pairs with values that meet a specified condition.

For example,

We start by importing the java.util.HashMap and java.util.Iterator packages, which provide the HashMap class needed to create and manipulate the map and the Iterator class for iterating through the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We create an iterator for the entry set of the map using the iterator() method.
We iterate through the map using a while loop. For each key-value pair, we check if the value meets a specified condition (e.g., if the length of the string is 3).
If the condition is met, we use the remove() method of the iterator to remove the key-value pair from the map.
We print the contents of the map to the console using a for loop and System.out.println to verify that the key-value pairs have been removed.

Java Program

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");
        myMap.put(4, "four");

        // Remove key-value pairs where value length is 3
        Iterator<Map.Entry<Integer, String>> iterator = myMap.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, String> entry = iterator.next();
            if (entry.getValue().length() == 3) {
                iterator.remove();
            }
        }

        // Print the contents of the map
        for (Map.Entry<Integer, String> entry : myMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

3: three
4: four

Summary

In this tutorial, we learned How to Remove Key-Value Pairs from a Map Based on Values in Java language with well detailed examples.

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How to Remove Key-Value Pairs from a Map Based on Values in Java