Reflection, as the name suggests, is an API(Application programming interface) functionality in JAVA via which the runtime instance of the class can be fully examined. It is a part of the Java.lang.reflect package. This package has to be imported at the start of the program, and then functions are invoked to understand the functionality of “reflection.” Any class’s behavior can be studied; metadata can be extracted or modified using reflection API in runtime.
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The syntax of common functions under reflection API to extract the class information is provided below:
The reflection class uses different methods defined in the Java.lang.reflect package to extract the class information. The information about class can be extracted using getClass() method, Constructors using getConstructors() method and methods using getMethods() method. These methods are defined in reflection API but return the class’s information, including methods, constructors, and more. Reflection API is used in JAVA programs, IDEs (Integrated development environment) like the eclipse, Netbeans. This can be well understood with the help of examples provided in the below section.
Different examples are mentioned below:
Code:
//package test; import java.lang.Class; public class test{ public static void main(String args[]){ Class<Boolean> c1 = boolean.class; System.out.println("Here, the class name is: "+c1.getName()); Class<test> c2 = test.class; System.out.println("This is another instance of class is used to derive class name : "+c2.getName()); } }
Output:
Explanation: Please check the example provided above. This has a package that contains all the classes named “test.” The test package has a class “test declared.” This class also contains the main method from which the execution of the program will start. The class “Class
In the next line, rather than using a primitive data type, a user-defined data type “class” named “test” is taken into consideration to extract the data. “Class
Code:
//package test; import java.lang.Class; class Simple{} public class test{ public static void main(String args[]){ try{ Class<?> c=Class.<em>forName</em>("Simple"); System.<em>out</em>.println("The result is: "+c.isInterface()); }catch(Exception e){System.<em>out</em>.println(e);} } }
Output:
Explanation: In the above example, a package is created named” test,” as created in the previous example number 1. This package contains a class name “Simple,” which is not the main class. The main class here is the “test” class which contains the main method from which the execution of the program will start. The “class >” is an identifier of reflection class which was instantiated via an object named “c” here. Then this object is used to pull out the decision indicator (True or false) of the function named “isInaterface.” This function pulls in a class as a parameter; in this case, the class which was pulled in as a parameter was the “Simple” class. This class is not an interface, so the “false” is returned as a result in the output screen. To invoke this function, the class object “c” was used.
Some of the advantages of using reflection in JAVA are listed below:
JAVA reflection makes it possible to introspect the classes, interfaces, methods, and more without knowing the class name at all. This all is done during compile time. This is considered as one of the most powerful properties of JAVA as this can be used to create instances of the class, and private members of the class can be extracted out using this. Developers can use this during runtime and for database-object mapping too.
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