How to remove an entry from HashMap by comparing values in Java 8

In this article, we will discuss how to remove an entry or entries from HashMap using Java 8 APIs

Before proceeding further, it is recommended to understand few terms w.r.t Map

• What is Map
• HashMap and its methods
• What is an Entry or Key-Value pairs in Map or HashMap

 

Remove entry/entries using removeIf() method by comparing values :

• removeIf(); –> Removes all of the elements of this collection that satisfy the given predicate
• Syntax:

  default boolean removeIf(Predicate<? super E> filter)
  

• We will cover different cases to remove entry/entries using removeIf() method of Java 8

 

Example 1: removing an entry using Equal-To operator (==)

RemovingEntryFromHashMap.java

package in.bench.resources.map.java8.example;

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

public class RemovingEntryFromHashMap {

	public static void main(String[] args) {

		// create HashMap
		Map<String, Integer> map = new HashMap<String, Integer>();

		// put few items
		map.put("Sachin", 200);
		map.put("Afrifi", 27);
		map.put("Pietersen", 104);
		map.put("Lara", 131);
		map.put("Ponting", 168);

		// printing map before removeIf
		System.out.println("Before removing entry from Map : \n"
				+ map);

		// removing an Entry using Java 1.8 (boolean equalTo expression) 
		map.entrySet().removeIf(
				matches -> matches.getValue()
				.compareTo(Integer.valueOf(27)) == 0);

		// printing map after removeIf
		System.out.println("\n\nAfter removing entry from Map : \n"
				+ map);
	}
}

Output:

Before removing entry from Map : 
{Lara=131, Afrifi=27, Pietersen=104, Ponting=168, Sachin=200}


After removing entry from Map : 
{Lara=131, Pietersen=104, Ponting=168, Sachin=200}

 

Example 2: removing all entries using Less-Than operator (<)

RemovingAllEntriesLessThan.java

package in.bench.resources.map.java8.example;

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

public class RemovingAllEntriesLessThan {

	public static void main(String[] args) {

		// create HashMap
		Map<String, Integer> map = new HashMap<String, Integer>();

		// put few items
		map.put("Sachin", 200);
		map.put("Afrifi", 27);
		map.put("Pietersen", 104);
		map.put("Lara", 131);
		map.put("Ponting", 168);

		// printing map before removeIf
		System.out.println("Before removing entry from Map : \n" 
				+ map);

		// removing all entries less-than 120 matches
		map.entrySet().removeIf(
				matches -> matches.getValue()
				.compareTo(Integer.valueOf(120)) < 0);

		// printing map after removeIf
		System.out.println("\n\nAfter removing entry from Map : \n" 
				+ map);
	}
}

Output:

Before removing entry from Map : 
{Lara=131, Afrifi=27, Pietersen=104, Ponting=168, Sachin=200}


After removing entry from Map : 
{Lara=131, Ponting=168, Sachin=200}

 

Example 3: removing all entries using Greater-Than operator (>)

RemovingAllEntriesGreaterThan.java

package in.bench.resources.map.java8.example;

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

public class RemovingAllEntriesGreaterThan {

	public static void main(String[] args) {

		// create HashMap
		Map<String, Integer> map = new HashMap<String, Integer>();

		// put few items
		map.put("Sachin", 200);
		map.put("Afrifi", 27);
		map.put("Pietersen", 104);
		map.put("Lara", 131);
		map.put("Ponting", 168);

		// printing map before removeIf
		System.out.println("Before removing entry from Map : \n"
				+ map);

		// removing all entries greater-than 150 matches
		map.entrySet().removeIf(
				matches -> matches.getValue()
				.compareTo(Integer.valueOf(150)) > 0);

		// printing map after removeIf
		System.out.println("\n\nAfter removing entry from Map : \n"
				+ map);
	}
}

Output:

Before removing entry from Map : 
{Lara=131, Afrifi=27, Pietersen=104, Ponting=168, Sachin=200}


After removing entry from Map : 
{Lara=131, Afrifi=27, Pietersen=104}

 

In the next article, we will discuss how to remove entry/entries from HashMap by comparing values using Java 8 APIs

 

Hope, you found this article very helpful. If you have any suggestion or want to contribute any other way or tricky situation you faced during Interview hours, then share with us. We will include that code here

 

Happy Coding !!
Happy Learning !!