Recursion is one of the tough programming technique to master. Many programmers working on both Java and other programming language like C or C++ struggles to think recursively and figure out recursive pattern in problem statement, which makes it is one of the favorite topic of any programming interview. If you are new in Java or just started learning Java programming language and you are looking for some exercise to learn concept of recursion than this tutorial is for you. In this programming tutorial we will see couple of example of recursion in Java programs and some programming exercise which will help you to write recursive code in Java e.g. calculating Factorial, reversing String and printing Fibonacci series using recursion technique. For those who are not familiar with recursion programming technique here is the short introduction: "Recursion is a programming technique on which a method call itself to calculate result". Its not as simple as it look and mainly depends upon your ability to think recursively. One of the common trait of recursive problem is that they repeat itself, if you can break a big problem into small junk of repetitive steps then you are on your way to solve it using recursion.
What Every Programmers Should know about Overriding equals and hashCode method in Java and Hibernate Example Tips and Best Practices
Override equals and hashCode in Java
Equals and hashCode in Java are two fundamental method which is declared in Object class and part or core Java library. equals() method is used to compare Objects for equality while hashCode is used to generate an integer code corresponding to that object. equals and hashCode has used extensively in Java core library like they are used while inserting and retrieving Object in HashMap, see how HashMap works in Java for full story, equals method is also used to avoid duplicates on HashSet and other Set implementation and every other place where you need to compare Objects. Default implementation of equals() class provided by java.lang.Object compares memory location and only return true if two reference variable are pointing to same memory location i.e. essentially they are same object. Java recommends to override equals and hashCode method if equality is going to be define by logical way or via some business logic and many classes in Java standard library does override it e.g. String overrides equals, whose implementation of equals() method return true if content of two String objects are exactly same. Integer wrapper class overrides equals to perform numerical comparison etc.
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