{"id":27553,"date":"2019-06-02T09:40:27","date_gmt":"2019-06-02T09:40:27","guid":{"rendered":"https:\/\/www.testingdocs.com\/questions\/?p=27553"},"modified":"2025-06-02T09:44:29","modified_gmt":"2025-06-02T09:44:29","slug":"what-is-a-nested-interface-in-java","status":"publish","type":"post","link":"https:\/\/www.testingdocs.com\/questions\/what-is-a-nested-interface-in-java\/","title":{"rendered":"What is a Nested Interface in Java?"},"content":{"rendered":"<h1>What is a Nested Interface in Java?<\/h1>\n<p>This blog will help you understand what nested interfaces are, why they\u2019re useful, and how they differ from nested classes.<\/p>\n<h2>Nested Interface<\/h2>\n<ul>\n<li>A<strong> nested interface<\/strong> is an interface that is declared inside another class or interface.<\/li>\n<li>It is a static interface by default.<\/li>\n<li>Nested interfaces can be accessed using the outer class or interface name.<\/li>\n<li>They help logically group interfaces that are only used by their outer class or interface.<\/li>\n<li>They can be declared <strong>public<\/strong>, <strong>private<\/strong>, or <strong>protected<\/strong> depending on their enclosing class.<\/li>\n<\/ul>\n<h2>Example of Nested Interface<\/h2>\n<pre><code class=\"\" data-line=\"\">\nclass OuterClass {\n    interface NestedInterface {\n        void display();\n    }\n}\n\nclass InnerClass implements OuterClass.NestedInterface {\n    public void display() {\n        System.out.println(&quot;This is a nested interface example.&quot;);\n    }\n}\n\npublic class Main {\n    public static void main(String[] args) {\n        OuterClass.NestedInterface obj = new InnerClass();\n        obj.display();\n    }\n}\n<\/code><\/pre>\n<h2><\/h2>\n<h2>Uses of Nested Interface<\/h2>\n<ul>\n<li><strong>Encapsulation:<\/strong> Groups related interfaces with the classes they belong to.<\/li>\n<li><strong>Modularity:<\/strong> Keeps the code organized and readable.<\/li>\n<li><strong>Access Control:<\/strong> Provides the ability to restrict access to the interface.<\/li>\n<li><strong>Namespace Management:<\/strong> Prevents name clashes by placing the interface in a specific scope.<\/li>\n<\/ul>\n<h2>Difference between Nested Interface and Nested Class<\/h2>\n<table border=\"1\" cellspacing=\"0\" cellpadding=\"8\">\n<thead>\n<tr>\n<th><\/th>\n<th>Nested Interface<\/th>\n<th>Nested Class<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Definition<\/td>\n<td>An interface declared inside a class or interface.<\/td>\n<td>A class declared inside another class.<\/td>\n<\/tr>\n<tr>\n<td>Type<\/td>\n<td>Always static by nature.<\/td>\n<td>Can be static or non-static (inner class).<\/td>\n<\/tr>\n<tr>\n<td>Implementation<\/td>\n<td>Implemented by a class using OuterClass.InterfaceName syntax.<\/td>\n<td>Instantiated using the outer class object (if non-static).<\/td>\n<\/tr>\n<tr>\n<td>Use Case<\/td>\n<td>To define a contract specific to the outer class or interface.<\/td>\n<td>To group helper classes or for logic encapsulation.<\/td>\n<\/tr>\n<tr>\n<td>Inheritance<\/td>\n<td>Only methods \u2014 no concrete behavior.<\/td>\n<td>Can have fields and concrete methods.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is a Nested Interface in Java? This blog will help you understand what nested interfaces are, why they\u2019re useful, and how they differ from nested classes. Nested Interface A nested interface is an interface that is declared inside another class or interface. It is a static interface by default. Nested interfaces can be accessed [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[40],"tags":[],"class_list":["post-27553","post","type-post","status-publish","format-standard","hentry","category-java","has-post-title","has-post-date","has-post-category","has-post-tag","has-post-comment","has-post-author",""],"_links":{"self":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/27553","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/comments?post=27553"}],"version-history":[{"count":7,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/27553\/revisions"}],"predecessor-version":[{"id":27560,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/27553\/revisions\/27560"}],"wp:attachment":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/media?parent=27553"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/categories?post=27553"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/tags?post=27553"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}