Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 14 | Java
14.5 Explain what object reflection is in Java and why it is useful.
pg 78
SOLUTION
Object Reflection is a feature in Java which provides a way to get reflective information about
Java classes and objects, such as:
1. Getting information about methods and fields present inside the class at run time.
2. Creating a new instance of a class.
3. Getting and setting the object fields directly by getting field reference, regardless of
what the access modifier is.
1 import java.lang.reflect.*;
2
3 public class Sample {
4 public static void main(String args[]) {
5 try {
6 Class c = Class.forName(“java.sql.Connection”);
7 Method m[] = c.getDeclaredMethods();
8 for (int i = 0; i < 3; i++) {
9 System.out.println(m[i].toString());
10 }
11 } catch (Throwable e) {
12 System.err.println(e);
13 }
14 }
15 }
This code’s output is the names of the first 3 methods inside the “java.sql.Connection” class
(with fully qualified parameters).
Why it is useful:
1. Helps in observing or manipulating the runtime behavior of applications.
2. Useful while debugging and testing applications, as it allows direct access to methods,
constructors, fields, etc.
2 2 9
Cracking the Coding Interview | Knowledge Based