{"id":663,"date":"2017-05-05T08:40:17","date_gmt":"2017-05-05T08:40:17","guid":{"rendered":"http:\/\/www.testingdocs.com\/questions\/?p=663"},"modified":"2025-06-02T07:34:19","modified_gmt":"2025-06-02T07:34:19","slug":"what-is-java-reflection","status":"publish","type":"post","link":"https:\/\/www.testingdocs.com\/questions\/what-is-java-reflection\/","title":{"rendered":"What is Java Reflection?"},"content":{"rendered":"

What is Java Reflection?<\/h1>\n

Java Reflection<\/strong> is a powerful feature in the Java programming language that allows a program to inspect and manipulate the runtime behavior<\/strong> of classes, methods, fields, and constructors \u2014 even if they are private<\/strong>.<\/p>\n

Java Reflection<\/strong> is a mechanism for manipulating classes, interfaces, and objects at the runtime of the Java program. Reflection API consists of methods to introspect the class at runtime.<\/p>\n

Features of Java Reflection<\/h2>\n

Using Reflection you can create an instance of a class whose name is not known until runtime. Invoke methods on an object, set and get accessors and mutators for an object’s field which is unknown until runtime.<\/p>\n

    \n
  • Inspect classes, interfaces, fields, and methods<\/strong> at runtime.<\/li>\n
  • Create objects<\/strong>, invoke methods<\/strong>, and access fields<\/strong> dynamically.<\/li>\n
  • Allows working with classes unknown at compile time<\/strong>.<\/li>\n
  • Can bypass access control checks<\/strong>, such as accessing private fields or methods.<\/li>\n<\/ul>\n

     <\/p>\n

    \"Java<\/p>\n

    java.lang.reflect<\/code> Package<\/h2>\n

    To import and use Reflection API we have to use the below statement.<\/p>\n

    import java.lang.reflect.*;<\/strong><\/p>\n

      \n
    • Class<\/code><\/li>\n
    • Method<\/code><\/li>\n
    • Field<\/code><\/li>\n
    • Constructor<\/code><\/li>\n
    • Modifier<\/code><\/li>\n<\/ul>\n

      Class object<\/strong><\/h2>\n

      For every loaded class, the Java Runtime Environment maintains an associated Class object. The Class object \u201creflects\u201d the class it represents You can use the Class object to discover information about a loaded class
      \n\u2022 name
      \n\u2022 modifiers
      \n\u2022 superclasses
      \n\u2022 implemented interfaces
      \n\u2022 fields
      \n\u2022 methods
      \n\u2022 constructors<\/p>\n

      Sample ways to access the Class object for a loaded class<\/p>\n

      To get the Class object for an object notKnownAtRuntime<\/strong><\/p>\n

      Class clz = notKnownAtRuntime.getClass();<\/strong><\/p>\n

      Dynamic Class loading<\/h2>\n

      The Class.forName(“classname”)<\/strong> method in Java is used to dynamically load a class at runtime.<\/p>\n

      Syntax:<\/strong><\/p>\n

      Class.forName(“fully.qualified.ClassName”);<\/strong><\/p>\n

      It loads the class specified by the string name.<\/p>\n

      It initializes the class (runs the static block and static initializations).<\/p>\n

      It returns the Class object associated with the class.<\/p>\n

      Example:<\/p>\n

      Class clz = Class.forName(\u201ccom.testingdocs.sample.program.SampleClass\u201d);<\/strong><\/p>\n

       <\/p>\n

      Java Program<\/strong><\/h2>\n

      In the below program we will print all the method names of Object class.<\/p>\n

      import java.lang.reflect.*; \n\npublic class ReflectionExample { \n\npublic static void main(String[] args) { \ntry { \n    Object obj = new Object(); \n     printMethodNames(obj); \n    } \ncatch (Exception e) { \n    System.out.println(e); \n   } \n}<\/code><\/pre>\n
      <\/pre>\n
      static void printMethodNames(Object o) { \n\nClass<?> c = o.getClass(); \nSystem.out.println("Method names of :" + c.getName() + " class"); \n\nMethod[] methods = c.getMethods(); \nfor (int i = 0; i < methods.length; i++) { \n    String methodName = methods[i].getName();                                \n    System.out.println(methodName + "()");\n    }\n } \n}<\/code><\/pre>\n
       <\/p>\n
      Program output<\/strong><\/h2>\n
      Method names of :java.lang.Object class
      \nwait()
      \nwait()
      \nwait()
      \nequals()
      \ntoString()
      \nhashCode()
      \ngetClass()
      \nnotify()
      \nnotifyAll()<\/p>\n
       <\/p>\n
      \"Java<\/p>\n","protected":false},"excerpt":{"rendered":"
      What is Java Reflection? Java Reflection is a powerful feature in the Java programming language that allows a program to inspect and manipulate the runtime behavior of classes, methods, fields, and constructors \u2014 even if they are private. Java Reflection is a mechanism for manipulating classes, interfaces, and objects at the runtime of the Java […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[40],"tags":[],"class_list":["post-663","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\/663","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=663"}],"version-history":[{"count":17,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/663\/revisions"}],"predecessor-version":[{"id":27552,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/663\/revisions\/27552"}],"wp:attachment":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/media?parent=663"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/categories?post=663"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/tags?post=663"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}