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Initialize a static Map using Stream in Java

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  • Last Updated : 29 Oct, 2021

In this article, a static map is created and initialized in Java using Stream.

Static Map in Java
A static map is a map which is defined as static. It means that the map becomes a class member and can be easily used using class.

Stream In Java
Introduced in Java 8, the Stream API is used to process collections of objects. A stream is a sequence of objects that supports various methods which can be pipelined to produce the desired result.

Approach:

  • Create a stream and insert 2D values as Key and Value pair in it.
  • These values will be later used to instantiate the Map.
  • Using the collect() method of Stream, map the values from the stream to the map.
  • This can be done with the help of Collectors.toMap() method and the keyMapper and ValueMapper respectively.

Below is the implementation of the above approach:




// Java program to create a static map using Stream
  
import java.util.*;
import java.util.stream.Collectors;
  
class GFG {
  
    // Declaring and instantiating the static map
    private static Map<String, String> map
        = Arrays.stream(new String[][] {
                            { "1", "GFG" },
                            { "2", "Geek" },
                            { "3", "GeeksForGeeks" } })
              .collect(Collectors.toMap(
                  keyMapper -> keyMapper[0], valueMapper -> valueMapper[1]));
  
    // Driver code
    public static void main(String[] args)
    {
        System.out.println(map);
    }
}

Output:

{1=GFG, 2=Geek, 3=GeeksForGeeks}

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