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Initialize a static Map using Java 9 Map.of()

  • Last Updated : 27 Nov, 2019

In this article, a static map is created and initialised in Java using Java 9.

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.

Java 9 feature – Map.of() method
In Java 9, Map.of() was introduced which is a convenient way to create instances of Map interface. It can hold up to 10 key-value pairs.

Approach:

  • Pass the map values as Key and Value pair in he Map.of() method.
  • A static factory Map instance is returned.
  • Store it in Map and use.

Below is the implementation of the above approach:



Example 1:




// Java program to create a static map using Java 9
  
import java.util.*;
  
class GFG {
  
    // Declaring and instantiating the static map
    private static Map<String, String> map
        = Map.of("1", "GFG",
                 "2", "Geek",
                 "3", "GeeksForGeeks");
  
    // Driver code
    public static void main(String[] args)
    {
        System.out.println(map);
    }
}

Output:

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

Example 2: To show the error when 10 key-value pairs are given




// Java program to create a static map using Java 9
  
import java.util.*;
  
class GFG {
  
    // Declaring and instantiating the static map
    private static Map<String, String> map
        = Map.of("1", "GFG",
                 "2", "Geek",
                 "3", "GeeksForGeeks",
                 "4", "G",
                 "5", "e",
                 "6", "e",
                 "7", "k",
                 "8", "s",
                 "9", "f",
                 "10", "o");
  
    // Driver code
    public static void main(String[] args)
    {
        System.out.println(map);
    }
}

Output:

{10=o, 9=f, 8=s, 7=k, 6=e, 5=e, 4=G, 3=GeeksForGeeks, 2=Geek, 1=GFG}

Example 3: To show the error when more than 10 key-value pairs are given




// Java program to create a static map using Java 9
  
import java.util.*;
  
class GFG {
  
    // Declaring and instantiating the static map
    private static Map<String, String> map
        = Map.of("1", "GFG",
                 "2", "Geek",
                 "3", "GeeksForGeeks",
                 "4", "G",
                 "5", "e",
                 "6", "e",
                 "7", "k",
                 "8", "s",
                 "9", "f",
                 "10", "o",
                 "11", "r");
  
    // Driver code
    public static void main(String[] args)
    {
        System.out.println(map);
    }
}

Compilation Error:

Main.java:12: error: no suitable method found for
 of(String, String,
    String, String,
    String, String,
    String, String,
    String, String,
    String, String,
    String, String,
    String, String,
    String, String,
    String, String,
    String, String)
        
1 error

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