10 Exception handling Best Practices in Java Programming

Exception handling is an important part of writing robust Java applications. It’s a non-functional requirement for any application, to gracefully handle any erroneous condition like resource not available, invalid input, null input, and so on. Java provides several exception handling features, in built-in the language itself in form of try, catch, and finally keyword.  Java programming language also allows you to create new exceptions and throw them using  throw and throws keyword. In reality, Exception handling is more than knowing the syntax. Writing a robust code is an art more than science, and here we will discuss few Java best practices related to Exception handling.

How to Fix Exception in thread "main" java.lang.ExceptionInInitializerError in Java Program? Example

JVM throws java.lang.ExceptionInInitializerError, when there is an Exception inside static initializer block. If you know about static variables in Java, then you may know that they are initialized at the time of class loading. If there is an Exception during that initialization of static variables, you will see ExceptionInInitializerError in Java. This could be any exception e.g. java.lang.ArrayIndexOutOfBound or java.lang.NullPointerException. Java developers are often confused with this error because they think that they have not defined any static initializer block, then how come they are getting ExceptionInInitializerError; well, by default Java combines all static variable initialization inside a static initializer block and initialize them in the order they are declared in the source file.

How to fix java.io.FileNotFoundException: (Access is denied)? Example

Earlier my impression was that java.io.FileNotFoundException: (Access is denied) comes when you try to read a text or binary file for which you don't have permission from the Java program but this can also come while you are using the jar command. jar command internally uses java.util.zip.ZipFile class to open any jar or war file which can throw java.io.FileNotFoundException: (Access is denied). I was trying to see the contents of the war file which was created using a recent build when I stumble upon this error, see the exact command below:

test@dev454:war-store/target jar -tvf maven-eclipse-web-demo
java.io.FileNotFoundException: maven-eclipse-web-demo (Access is denied)
        at java.util.zip.ZipFile.open(Native Method)
        at java.util.zip.ZipFile.<init>(ZipFile.java:127)
        at java.util.zip.ZipFile.<init>(ZipFile.java:88)
        at sun.tools.jar.Main.list(Main.java:979)
        at sun.tools.jar.Main.run(Main.java:224)
        at sun.tools.jar.Main.main(Main.java:1149)

How to resolve java.lang.UnsupportedClassVersionError:Unsupported major.minor version 49.0 to 65 with example

The java.lang.UnsupportedClassVersionError  is a quite common error after NoClassDefFoundError or ClassNotFoundException they all seems to related to class files but they all are different and there cause and resolution are different. In this java tutorial, we will see what is UnsupportedClassVersionError in Java? Why UnsupportedClassVersionError comes in Java? What are a class file format and version numbers associated with it and finally how to resolve UnsupportedClassVersionError in Java? 

Fixing java.net.BindException: Cannot assign requested address: JVM_Bind in Tomcat, Jetty

One of the most dreaded errors in Java-based client server-based applications is a networking-related error, e.g. java.net.BindException: Cannot assign requested address: JVM_Bind. I have faced this issue while working with web servers like Tomcat, Jetty, and Weblogic before, but yesterday it came again when one of my colleagues faced this issue in Windows. As soon as Java programmers see java.net.BindException, they come to the conclusion that it's an issue with two processes listening on the same port and often mistook it for Java.net.BindException: Address already in use: JVM_Bind:8080, which is slightly different than this.

How to Fix java.net.ConnectException: Connection refused: connect in Java

java.net.ConnectException: Connection refused: connect is one of the most common networking exceptions in Java. This error comes when you are working with client-server architecture and trying to make a TCP connection from the client to the server. Though this is not as cryptic as java.lang.OutOfMemoryError: Java heap space or java.lang.UnsupportedClassVersionError, it’s still a frequent problem in distributed Java applications. java.net.ConnectException: Connection refused: connect also comes in the case of RMI (Remote Method Invocation) because RMI also uses TCP-IP protocol underneath. While writing client socket code in Java, You should always provide proper handling of this exception. 

How to solve java.util.NoSuchElementException in Java? Example

How to fix java.util.NoSuchElementException in Java

java.util.NoSuchElementException is a RuntimeException that can be thrown by different classes in Java like Iterator, Enumerator, Scanner, or StringTokenizer. All of those classes have a method to fetch the next element or next tokens if the underlying data structure doesn't have any element Java throws "java.util.NoSuchElementException". The most common example of this is iterating over hashmap without checking if there is an element or not and that's why it's advised to use hashNext() before calling next() on Iterator. In this Java tutorial we will what causes NoSuchElementException in Java and how to avoid it completely.

How to fix java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory

java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory or "Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory" exception comes when you don't apache commons-logging-1.1.1.jar in your Classpath. I have faced this exception many times while using open-source frameworks like Struts, Spring, and Displaytag which uses a commons-logging framework for logging. commons-logging is not an actual java logging framework but provides a wrapper so that you can use log4j, java logging, or any other Java logging framework.

[Solved] How to find and Print Armstrong number between 0 and 9999 in Java? Example

An Armstrong number of three digits is an integer such that the sum of the cubes of its digits is equal to the number itself. For example, 153 is an Armstrong number, since 1**3 + 5**3 + 3**3 = 153, 371 is an Armstrong number since 3**3 + 7**3 + 1**3 = 371. Along with usual beginner exercises like calculating factorial, reversing a string, or calculating prime numbers, this is a good exercise to build programming logic. It teaches you basic programming techniques of how to use the operator for something which is not obvious.

Java Program to Multiply Two Matrices - Matrix Multiplication Example

How to write a Java program to multiply two matrices in Java is a very good programming exercise to get familiar with the two-dimensional array in Java. this example teaches about how to multiply arrays, how to access elements from a multi-dimensional array, how to pass them to a function etc. Since the matrix is a natural representation of a multi-dimensional array in Java, they are often used to illustrate real word matrix exercises e.g. the calculating sum of two matrices or calculating the difference of two matrices, etc. It's also one of the popular Matrix based coding problems you can find on coding interviews. 

[Solved] How to Implement Binary Search in Java without Recursion? Iterative Algorithm Example Tutorial

Hey Java programmers, if you want to implement a binary search in Java, and looking for both iterative and recursive binary search algorithms then you have come to the right place. Earlier, I have shared the free courses to learn Data Structure and algorithms in Java, and today, I am going to teach you an important algorithm.  In computer science, a binary search or half-interval search is a divide and conquer algorithm which locates the position of an item in a sorted array. Binary search works by comparing an input value to the middle element of the array. The comparison determines whether the element equals the input, less than the input or greater. 

How to Implement Stack data structure in Java? Example Tutorial

The stack is one of the popular data structures which supports LIFO (Last In First OUT) operation. Due to the LIFO advantage, you can use a stack data structure to convert a recursive algorithm to an iterative one. The stack data structure is very easy to implement using an array or linked list, but you don't have to implement it on your own because Java already provides a Stack implementation in java.util.Stack class. This class is a subclass of the Vector class and you should use it whenever you need Stack for your production code, there is no point in inventing the wheel again when the focus is on developing your application.

How to check if a given Number is Binary in Java? [Solved] Example

Today we will take a look at another simple programming exercise, write a program to check if a number is binary in Java. A number is said to be binary if it only contains either 0 or 1, for example, 1010 is a binary number but 1234 is not. You can not any library method to solve this problem, you need to write a function to check if the given number is binary, you can use basic constructs of Java programming language e.g. operators, keywords, control statements, etc. If you are a regular reader of Javarevisited, then you know that I love to share simple programming problems here.

How to find Middle Element of Linked List in Java in Single Pass

ow do you find the middle element of LinkedList in one pass is a programming question often asked Java and non-Java programmers in telephonic Interview. This question is similar to checking palindrome or calculating the factorial, where the Interviewer sometimes also asks to write code. In order to answer this question candidate must be familiar with the LinkedList data structure i.e. In the case of the singly LinkedList, each node of Linked List contains data and pointer, which is the address of the next Linked List and the last element of Singly Linked List points towards the null. Since in order to find the middle element of the Linked List you need to find the length of the linked list, which is counting elements till the end i.e. until you find the last element of the Linked List.

How to find the 3rd (Kth) Node from end of linked list in Java? Fast and Slow Pointer Example [Solved]

Hello guys, the problem to find the 3rd element from the end in a singly linked list or Kth node from the tail is one of the tricky but frequently asked linked list problems in Programming job interviews. I know you can easily solve this problem by moving from tail to head or in the reverse direction but the main challenge here is to solve the problem in just one pass. That means, you can not traverse the linked list again and you cannot traverse backward because it's a singly linked list. So what do you think? Isn't this problem challenging? Well, I did struggle when I saw this problem very first time but once you understand the logic and some tricks to solve a linked list based problem like Recursion then it would be easy for you, and that's what you will learn in this article.