How to iterate Map in Java

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Last updated on June 7th, 2024

In this topic, we will learn to iterate the Map in Java. A Map is an interface that is available in java.util package. These are the following ways to iterate the Map:
• Iterate Map Using Iterator
• Iterate Map Using for each loop
• Iterating Map using keySet() and values() methods
• Iterate Map using forEach() method

Iterate Map Using Iterator

Example

import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
public class Test
{
public static void main(String[] arg)
{
Map<Integer,String> map = new HashMap<Integer,String>();
        map.put(1, "Peter");
        map.put(2, "Robert");
        map.put(3, "William");
        map.put(4, "John");
        // Using iterator
        Iterator<Map.Entry<Integer, String>> itr = gfg.entrySet().iterator();
       while(itr.hasNext())
        {
             Map.Entry<Integer, String> entry = itr.next();
             System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
        }
    }
}

Output

Key = 1, Value = Peter
Key = 2, Value = Robert
Key = 3, Value = William
Key = 4, Value = John

Iterate Map Using for each loop

Example

import java.util.Map;
import java.util.HashMap;
public class Test
{
 public static void main(String[] arg)
    {
        Map<Integer,String> map = new HashMap<Integer,String>();
        map.put(1, "Peter");
        map.put(2, "Robert");
        map.put(3, "William");
        map.put(4, "John");
        
       for(Map.Entry<Integer,String> entry:map.entrySet())
        {
         System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
        }
    }
}

Output

Key = 1, Value = Peter
Key = 2, Value = Robert
Key = 3, Value = William
Key = 4, Value = John

Iterating Map using keySet() and values() methods

Example

import java.util.Map;
import java.util.HashMap;
public class Test
{
  public static void main(String[] arg)
   {
    Map<Integer,String> map = new HashMap<Integer,String>();
      
        map.put(1, "Peter");
        map.put(2, "Robert");
        map.put(3, "William");
        map.put(4, "John");

       // using keySet() for iteration over keys
        for (Integer key : map.keySet())
            System.out.println("key: " + key);
          
        // using values() for iteration over values
        for (String value : map.values()) 
            System.out.println("value: " + value);
    }
}

Output

key: 1
key: 2
key: 3
key: 4
value: Peter
value: Robert
value: William
value: John

Iterate Map using forEach() method

Example

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

public class Test
{
    public static void main(String[] arg)
    {
        Map<Integer,String> map = new HashMap<Integer,String>();
      
        map.put(1, "Peter");
        map.put(2, "Robert");
        map.put(3, "William");
        map.put(4, "John");
        
       // forEach(action) method to iterate map
       map.forEach((k,v) -> System.out.println("Key = "
                + k + ", Value = " + v));
    }
}

Output

Key = 1, Value = Peter
Key = 2, Value = Robert
Key = 3, Value = William
Key = 4, Value = John

Conclusion

In this topic, we learnt about how to iterate Map in several ways in Java.

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