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10 Example of netstat command in UNIX and Linux

The netstat command is one of the most essential and useful networking command for Linux users. It is a general, all purpose network information tool which can be used to find out information about current network connections, multicast group membership, routing tables, network interface statistics and many other low-level details of the host's current network configuration. The good knowledge of netstat command is not only important from the troubleshooting perspective but also from security perspective. It gives useful security related information e.g. what network ports are currently "open" on your system and the list of current network connections and their states. 

Template Method Design Pattern in Java? Example Tutorial

Template Method Pattern defines a sequence of steps of an algorithm but let you free to implement those steps on your way. You cannot change the algorithm but you can define how those steps should behave. To make sure that you cannot change the algorithm, template methods are usually made final in Java, which is also a good use case of when to make a method final in Java. The subclasses are still  allowed to override the steps but as I said, they are not allowed to change the sequence. It can also be provided a default implementation for one or more steps. Let us look at the following example to understand Template Method Pattern.  A Template method pattern provides a skeleton for performing any sort of algorithm or an operation, and it allows the sub-classes to re-define part of the logic

Top 50 Free Spring and Spring Boot Certification Practice Questions Answers for VMWARE EDU-1202 Exam

Hello guys, preparing for IT certification like Oracle's Java certification or Vmware's Spring Certification required a lot of hard-work. I have seen many experienced Java developers failing these certifications and losing money and time due to over-confidence and lack of preparation. A structured and complete certification preparation involves reading books, joining course and doing practice questions. When it comes to Spring certification, practice questions are quite hard to find and that's why I created my Udemy course with 250+ Spring Certification questions. This course has helped more than 9000 students in their Spring certification preparation journey. 

3 ways to parse JSON String to Object in Java [Jackson, Gson, and json-simple Example]

One of the common task in Java web application, particularly the ones which deals with RESTful web services are parsing JSON messages. Many times you need to parse JSON to create a Java object like parsing a JSON message to create a POJO,  for example, an Order or a Book. Representing JSON in Java is easy, it's like a String value but unfortunately, JDK doesn't provide any standard API to parse JSON in Java. There were talks to add JSON parsing API in JDK 9 but that didn't materialize, but you don't need to worry. There are many good open-source JSON parsing libraries you can use to parse any kind of JSON in your Java program. 

Is Java Pass by Value or Pass by Reference? Example

Hello guys, Does Java is pass by value or pass by reference is one of the tricky Java questions mostly asked on both beginner and experienced level Java developer interviews. Before debating whether Java is pass by value or pass by reference lets first clear what is pass by value and what is pass by reference actually means?. This question has its origin in C and C++ where you can pass function parameter either value or memory address, where value is stored (pointer). As per Java specification everything in Java is pass by value whether its primitive value or objects and it does make sense because Java doesn't support pointers or pointer arithmetic, Similarly multiple inheritance and operator overloading is also not supported in Java.

How to iterate over JSONObject in Java to print all key values? Example Tutorial

Hello guys, if you are wondering how to iterate over a JSONObject in Java and print all its fields and values then you have come to the right place. In this article, I will show you how you can print all data from JSONObject in Java. If you know, In json-simple library, one of the top 5 and lightweight JSON library, JSON object is a wrapper class which contains the actual JSON message. In the last article, I have explained how to parse JSON in Java using json-simple library and one question which pops up can we iterate over JSONObject properties? Well, yes, you can iterate over all JSON properties and also get the values from the JSONObject itself. In this article, I'll show you how you can print all keys and value from JSON message using JSONOjbect and Iterator.

How to merge two HashMap in Java 8 - Map.merge() example

Hello guys, if you are wondering how to merge two Map like two HashMap in Java then you have come to the right place. In this tutorial,  I will show you step by step to merge two HashMap in Java. You can merge two Map in Java using the newly added merge() function in Java 8. This allows you to copy values from one map to another to merge both of them. It also provide a lot of flexibility to handle duplicate keys. In the last article, I have shown you how to combine two Map in Java using the putAll() method but there was a problem. If a key is present in both maps, then putAll() overrides the value from the second map, which you may or may not want. 

12 Database SQL Index Interview Questions and Answers for 2 to 5 Years Experienced

A good understanding of Index is very important for any programmer working with database and SQL. It doesn't matter whether you are working as DBA or Application developer, working in Oracle, MySQL, or Microsoft SQL Server or any other database, you must have good understanding of how index works in general. You should know different types of index and their pros and cons, how your database or Query engine chooses indexes and the impact of table scan, index scan, and index seek. You should also be able to build upon your knowledge to optimize your SQL queries as well as troubleshoot a production issue involving long running queries or poor performing queries. This is also a great skill for experience developers with 5 to 6 years of experience under his belt. 

50+ Java Collections and Generics Interview Questions with Answers

Hello guys, If you are preparing for Java interviews then you may know that Java Generics and Collections are two of the most important topics, particularly Generics where some of the trickiest Java questions can be asked. They are also used to gauge your experience and depth of your Java knowledge, hence it's imperative for both beginners and experienced Java programmers to prepare this topic well. While the Java Collection framework provides an implementation of some command data structures like ListSetArray, Hash table, Queue, Stack, PriorityQueue, etc, Generics provides Type safety.

Java Consumer Functional Interface Example

A Java Consumer is a predefined function interface that has been introduced by java 8. This type of interface accepts only one argument in order to generate the result. We can use Consumer once an object is ready to be used, so we send the input and it executes some operation on the object without returning any kind of value. In the last few article, I have explained what is Functional interface and showed example of Predicate Interface and in this article, I will show you how to use Consumer functional Interface in Java. 

Top 40 Java HashMap Interview Questions and Answers for 3 to 5 Years Experienced

Hello guys, HashMap and ArrayList is two of the most useful classes from JDK and every Java programmer should be familiar with them. Because of their usefulness, they are also very popular on Java interviews. You will always find a couple of questions on HashMap, ArrayList and its close cousins like Hashtable and ConcurrentHashMap on various Java interviews, ranging from freshers to experienced, junior to senior programmers, and telephonic to face-to-face interviews. To help my readers to better prepare for Java interviews, I have shared some of the essential ArrayList interview questions in my last article and today I am going to share  frequently asked questions on Java HashMap.