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Java reflection supports dynamic retrieval of information about classes and data structures by name, and allows for their manipulation within an executing Java program.

Reflection is commonly used by programs which require the ability to examine or modify the runtime behavior of applications running in the Java virtual machine. It gives Java classes the ability to perform dynamic introspection: the ability to look inside classes that are already loaded.
Reflection API consists of two components: objects that represent the various parts of a class file, and a means for extracting those objects in a safe and secure way.

The first component of the Reflection API is the mechanism used to fetch information about a class. This mechanism is built into the class named Class. The special class Class is the universal type for the meta information that describes objects within the Java system. Class loaders in the Java system return objects of type Class. Up until now the three most interesting methods in this class were:

forName, which would load a class of a given name, using the current class loader

getName, which would return the name of the class as a String object,which was useful for identifying object references by their class name

newInstance, which would invoke the null constructor on the class (if it exists) and return you an object instance of that class of object


To these three useful methods the Reflection API adds some additional methods to class Class. These are as follows:

getConstructor, getConstructors, getDeclaredConstructor
getMethod, getMethods, getDeclaredMethods
getField, getFields, getDeclaredFields
getSuperclass
getInterfaces
getDeclaredClasses