In this post, we will learn how to create an immutable HashMap before Java 9 and using Java 9 provided Map.ofEntries() static factory method.
Create an Immutable HashMap Example
Refer the comments are self-descriptive.
package com.java.tutorials.java9; import java.util.Collections; import java.util.HashMap; import java.util.Map; public class ImmutableHashMap { public static void main(String[] args) { Map < String, String > fruits = new HashMap < String, String > (); fruits.put("1", "Banana"); fruits.put("2", "Mango"); fruits.put("3", "Apple"); // before java 9 fruits = Collections.unmodifiableMap(fruits); System.out.println(fruits); // java 9 with factory methods Map < String, String > map = Map.ofEntries( Map.entry("1", "Banana"), Map.entry("2", "Mango"), Map.entry("3", "Apple")); System.out.println(map); } }
Output:
{1=Banana, 2=Mango, 3=Apple}
{1=Banana, 2=Mango, 3=Apple}
References
Related HashMap Source Code Examples
HashMap
Java
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