Remove elements of map while iterating?

Approach 1: Using iterator

Iterator<Map.Entry<Integer, String>> iterator = map.entrySet().iterator();

while (iterator.hasNext()) {
 iterator.remove();
}

App.java

package com.sample.app;

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

public class App {

 public static void main(String[] args) {
  Map<Integer, String> map = new HashMap<>();

  map.put(1, "Krishna");
  map.put(2, "Ram");
  map.put(3, "Rahim");
  map.put(4, "Joel");

  System.out.println(map);

  System.out.println("Deleting all the entries in map whose key is even number");
  Iterator<Map.Entry<Integer, String>> iterator = map.entrySet().iterator();

  while (iterator.hasNext()) {
   int key = iterator.next().getKey();

   if (key % 2 == 0) {
    iterator.remove();
   }
  }

  System.out.println(map);

 }

}

Output

{1=Krishna, 2=Ram, 3=Rahim, 4=Joel}

Deleting all the entries in map whose key is even number

{1=Krishna, 3=Rahim}

Approach 2: Use removeIf function

‘removeIf’ function is added in Java8.

Example

map.entrySet().removeIf(entry -> entry.getKey() % 2 == 0);

App.java

package com.sample.app;

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

public class App {

 public static void main(String[] args) {
  Map<Integer, String> map = new HashMap<>();

  map.put(1, "Krishna");
  map.put(2, "Ram");
  map.put(3, "Rahim");
  map.put(4, "Joel");

  System.out.println(map);

  System.out.println("Deleting all the entries in map whose key is even number");

  map.entrySet().removeIf(entry -> entry.getKey() % 2 == 0);

  System.out.println(map);

 }

}

Output

{1=Krishna, 2=Ram, 3=Rahim, 4=Joel}

Deleting all the entries in map whose key is even number

{1=Krishna, 3=Rahim}

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