The Deet example searches for public methods in a class which begin with the string ' test ', have a boolean return type, and a single Locale parameter. This can be done through Java's reflective API. Consider a test suite which uses reflection to invoke private test methods in a given class. For example, let's say I want to perform type introspection on a method of String and then reflectively invoke it. What if I wanted to do something a bit more involved. The superclass of String is simply Object. I also get the superclass of String by calling getSuperclass(). String is defined as public and final as shown in the output above. getModifiers() provides the modifiers defined on the class. Once I have an instance of Class, getModifiers() is called on the class instance. It provides a Class instance, allowing for type introspection. getClass() is defined on Object, allowing access to the runtime class of any object. First the method getClass() is called on the object. This is a very simple example of type introspection, but you can see the power (yet relative simplicity) of. String modifier = Modifier.toString(objectClass.getModifiers()) Ĭlass superClass = objectClass.getSuperclass() For starters we can perform type introspection on this object with the help of Class. Let's say we created the string "1995" as an object in Java. To use type introspection along with the reflection API in Java, we have to utilize the class. This is a very basic example of type introspection. For example, the following code was run in JShell (the new Java REPL) to see what two different Object declarations were instantiated as. Examples of type introspection in Java include the instanceof operator and the Class class.īasic usage of the instanceof operator is to see if an object was instantiated as a certain type. Type introspection gives developers the ability to look at multiple aspects of objects at runtime, including the type, methods, instance variables, modifiers and more 2. The ability of a programming language to examine its objects at runtime.
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