Program to convert a Map to a Stream in Java

Last Updated : 11 Jul, 2025
A Stream is a sequence of objects that supports various methods which can be pipelined to produce the desired result. Below are various method to convert Map to Stream in Java:
  1. Converting complete Map<Key, Value> into Stream: This can be done with the help of Map.entrySet() method which returns a Set view of the mappings contained in this map. In Java 8, this returned set can be easily converted into a Stream of key-value pairs using Set.stream() method. Algorithm:
    1. Get the Map<Key, Value>.
    2. Convert Map<Key, Value> into Set<Key> using Map.entrySet() method.
    3. Convert the obtained Set into Stream using Set.stream()
    4. Return/Print the Stream of Map.
    Program: Java 
    // Java Program to convert
// Map<Key, Value> into Stream

import java.util.*;
import java.util.stream.*;

class GFG {

    // Generic function to convert List of
    // String to List of Integer
    public static <K, V> Stream<Map.Entry<K, V> >
    convertMapToStream(Map<K, V> map)
    {

        // Return the obtained Stream
        return map

            // Convert the Map to Set
            .entrySet()

            // Convert the Set to Stream
            .stream();
    }

    public static void main(String args[])
    {

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

        // Add entries to the Map
        map.put(1, "Geeks");
        map.put(2, "forGeeks");
        map.put(3, "A computer Portal");

        // Print the Map
        System.out.println("Map: " + map);

        // Convert the Map to Stream
        Stream<Map.Entry<Integer, String> > stream = 
                                   convertMapToStream(map);

        // Print the TreeMap
        System.out.println("Stream: " 
                      + Arrays.toString(stream.toArray()));
    }
}
    Output: 
    Map: {1=Geeks, 2=forGeeks, 3=A computer Portal}
Stream: [1=Geeks, 2=forGeeks, 3=A computer Portal]
  2. Converting only the Keyset of the Map<Key, Value> into Stream: This can be done with the help of Map.keySet() method which returns a Set view of the keys contained in this map. In Java 8, this returned set can be easily converted into a Stream of key-value pairs using Set.stream() method. Algorithm:
    1. Get the Map<Key, Value>.
    2. Convert Map<Key, Value> into Set<Key> using Map.keySet() method.
    3. Convert the obtained Set into Stream using Set.stream()
    4. Return/Print the Stream of Map.
    Program: Java 
    // Java Program to convert
// Map<Key, Value> into Stream

import java.util.*;
import java.util.stream.*;

class GFG {

    // Generic function to convert List of
    // String to List of Integer
    public static <K, V> Stream<K>
    convertMapToStream(Map<K, V> map)
    {

        // Return the obtained Stream
        return map

            // Convert the Map to Set<Key>
            .keySet()

            // Convert the Set to Stream
            .stream();
    }

    public static void main(String args[])
    {

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

        // Add entries to the Map
        map.put(1, "Geeks");
        map.put(2, "forGeeks");
        map.put(3, "A computer Portal");

        // Print the Map
        System.out.println("Map: " + map);

        // Convert the Map to Stream
        Stream<Integer> stream = convertMapToStream(map);

        // Print the TreeMap
        System.out.println("Stream: " 
                    + Arrays.toString(stream.toArray()));
    }
}
    Output: 
    Map: {1=Geeks, 2=forGeeks, 3=A computer Portal}
Stream: [1, 2, 3]
  3. Converting only the Value of the Map<Key, Value> into Stream: This can be done with the help of Map.values() method which returns a Set view of the values contained in this map. In Java 8, this returned set can be easily converted into a Stream of key-value pairs using Set.stream() method. Algorithm:
    1. Get the Map<Key, Value>.
    2. Convert Map<Key, Value> into Set<Value> using Map.values() method.
    3. Convert the obtained Set into Stream using Set.stream()
    4. Return/Print the Stream of Map.
    Program: Java 
    // Java Program to convert
// Map<Key, Value> into Stream

import java.util.*;
import java.util.stream.*;

class GFG {

    // Generic function to convert List of
    // String to List of Integer
    public static <K, V> Stream<V>
    convertMapToStream(Map<K, V> map)
    {

        // Return the obtained Stream
        return map

            // Convert the Map to Set<Value>
            .values()

            // Convert the Set to Stream
            .stream();
    }

    public static void main(String args[])
    {

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

        // Add entries to the Map
        map.put(1, "Geeks");
        map.put(2, "forGeeks");
        map.put(3, "A computer Portal");

        // Print the Map
        System.out.println("Map: " + map);

        // Convert the Map to Stream
        Stream<String> stream = convertMapToStream(map);

        // Print the TreeMap
        System.out.println("Stream: " 
                     + Arrays.toString(stream.toArray()));
    }
}
Output: 
Map: {1=Geeks, 2=forGeeks, 3=A computer Portal}
Stream: [Geeks, forGeeks, A computer Portal]
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