Tuesday, 17 October 2017

10 Points about Enum in Java

Apart from Class and Interface, Enumeration type or Enum is another popular type in Java programming language. Enum allows you to represent fixed number of things in a type-safe manner e.g. days of the week, days of the month, planets in solar system, buttons on remote control, keys on keyboard and suits on playing cards. Before Enum was introduced, prior to Java 1.5, integer and string constants are used to represent fixed number of things, known as enum int pattern and enum string pattern. Though they serve the purpose, they had some major drawbacks, one of them was type-safety i.e. you cannot restrict them to represent fixed number of values  e.g. an integer constant, which is representing days of the week can have value as 100, which is incorrect, given we have only 7 days in a week.

Monday, 16 October 2017

Oracle Java Variables

Variables


The variable is the basic unit of storage in a Java program. A variable is defined by the combination of an identifier, a type, and an optional initializer. In addition, all variables have a scope, which defines their visibility, and a lifetime. These elements are examined next.

Friday, 13 October 2017

Best way to convert java.util.Date to java.time.LocalDate in Java 8 - Examples

There seem to be a couple of ways to convert a java.util.Date to java.time.LocalDate in Java 8, but which one is the best way? We'll figure it out in this article, but first, let's explore these different ways to convert a java.util.Date object to LocalDate in Java 8. Btw, even though both Date and LocalDate is used to represent dates in Java they are not quite same, they don't contain even similar information. For example, the old Date class contains both date and time components but LocalDate is a just date, it doesn't have any time part in it e.g. "05-10-2017".

Wednesday, 11 October 2017

2 Ways to Print Custom String Value of Java Enum

We all know that how powerful enumeration type in Java is, and one of the main strength of enum is that they can implement an interface, they can have an instance variable and you can also override any method inside enum instance. In Java programs, we often need to convert Enum to String type, sometimes just to print values in log file and other time for storing log into database.  By default, when you print an enum constant, it print its literal value e.g. if name of enum instance is RED, then it will print RED. This is also the value which is returned by name() method of java.lang.Enum class.

Tuesday, 10 October 2017

Java Program to print prime numbers from 1 to 100

In this article, I'll share you a simple problem about writing a Java program to print prime numbers up to a given number e.g. say prime numbers from 1 to 100. It's one of the most common coding exercises for programmers learning in Java, as it gives you an opportunity to learn more about essential operator in Java Programming. The key here is that you cannot use a library function which can simply your job, you need to devise the algorithm for checking prime number by yourself. One of the most popular algorithm for generating prime is Sieve of Eratosthenes, which we have discussed earlier, but in this post, we will take a simpler approach. We'll first write a function to check whether a number is prime or not and then we loop through first 100 numbers i.e. from 1 to 100 and print only those which passed the prime test. Btw, if you are looking for some serious programming coding question for the interview, then you can also take a look at Cracking the coding interview, which contains more than 150 coding question with solutions.