Reflection in Java

Reflection is a feature in the Java programming language. For example, there is no way in a C, or C++ program to obtain information about the functions defined within that program. It is an API which is used to examine or modify the behavior of methods, classes and interfaces at runtime. Classes that are required in order to use reflection features are provided in java.lang.reflect package. Through reflection we can access the private variables and methods of a class with the help of its class object and invoke the method. Useful methods Methods that will allow us to get information about class itself:

int getModifiers();
        boolean isArray();
        boolean isEnum();
        boolean isInstance(Object obj);
        boolean isInterface();
        boolean isPrimitive()

If we want to get information about attributes we can use following methods:

Field getField(String name); // gets only public attribute
        Field[] getFields(); // gets only public attributes
        Field getDeclaredField(String name);
        Field[] getDeclaredFields();


To get reference of methods:
        Method getMethod(String name, Class<?>... parameterTypes);
And to invoke it:
        method.invoke(obj, arg1, arg2,...);

Advantages: * Debuggers utilize the property of reflection to look at private members on classes * Can dynamically obtain class instances at runtime, improve flexibility and dynamic compilation Disadvantages: * Performances - Reflective operations have slower performance than their non-reflective operations. * Traceability - It is hard to find where is an error if a reflective method call fails