L’autoboxing est la conversion automatique que le compilateur Java effectue entre les types primitifs et leurs classes d’encapsuleur d’objets correspondantes. Par exemple, convertir un int en un Integer, un double en un Double, etc. Si la conversion se déroule dans l’autre sens, cela s’appelle unboxing. Voici l’exemple le plus simple d’auto-boxe : Character ch = […]
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Java : How to Convert Integer to Binary
In Java, we can use Integer.toBinaryString(int) to convert an Integer to a binary string representative. This article will show you two methods to convert an Integer to a binary string representative. JDK Integer.toBinaryString. Old school bit masking technique. 1. Convert Int to Binary Integer.toBinaryString 1.1 This Java example tries to convert an int to a binary string […]
Java : How to Convert Character to ASCII
In Java, we can cast the char to int to get the ASCII value of the char. The explicit cast (int)char is optional, if we assign a char to an integer, Java will auto-cast the char to an int. 1. Convert Char to ASCII This Java example converts a char to an ASCII value, and […]
How to get the index of an element existing in ArrayList ?
indexOf : if you want to get the index of an object existing in Java ArrayList, you can use this method Predefined :
Solution Codingame : Arbre binaire Java – binary tree – Node.java
Solution : Main.java : Filling the binary tree to test…
Java : how to convert negative binary to Integer ?
Review the following Java example to convert a negative integer in binary string back to an integer type. The result is NumberFormatException ! The NumberFormatException is due to overflow, the string 11111111111111111111111111111111 (length of 32) are unable to fit into the 32 bits int type ? Note Note Integer has values from -2^31 to 2^31-1 […]
Comment retourner une chaîne simple en JSON dans Rest Controller ?
Format JSON RestController : Retournez text/plain (comme dans Renvoie uniquement le message de chaîne du contrôleur Spring MVC ) OR enroulez votre chaîne comme un objet. Définissez votre type de réponse sur application/json et vous aurez un JSON qui ressemble à
Solution : How to parse JSON in Java ?
Parse JSON in Java : I have the following JSON text. How can I parse it to get the values of … ? Solution :
Solution getClosestToZero.java : Java Program to Find the Integer number in given array that is closest to zero
It’s one of the most common Java interview questions !!! Let’s talk about this post. In this post, we will see how to write a Java program to find the Integer Number in a given array that is closest to zero. Mentioned below is the snippet from a hiring team. In the question, they stated […]
Exemple Singleton : Comment empêcher de lancer plusieurs fois simultanément une application Java ?
Comment empêcher de lancer plusieurs fois simultanément une application Java ? Par exemple, vous venez de programmer un serveur, vous voulez vous assurer qu’une seule instance est lancée, pour éviter de provoquer des comportements inattendus (une instance reçoit une requête d’un client, et l’autre reçoit son identifiant). En général, quel que soit le programme, il peut […]
“Auto increment” alphabet in Java ?
Auto increment alphabet in Java : There is two solution for auto increment alphabet using java : Solution 1 : Solution 2 : It is also possible with typecasting Read also : Java 7 – Java 8 – loop Map / List – forEach examples Read also : Twitter teste une façon de limiter les […]
Java : multi-line string, text blocks
Java multi-line string text blocks : This article will show you a few ways to declare and use a multi-line string in Java. String + String + String StringBuilder String.format StringWriter String.join (Java 8) Files.lines (Java 8) (“””) Java 13 and Java 14 text blocks (preview feature) Java multi-line string text blocks : Review an […]
Configurez Logback en Java
Afin de normaliser la configuration Logback des applications web sur lesquelles j’interviens, j’ai récemment eu besoin de programmer Logback via son API en Java et non en utilisant la syntaxe XML Joran.Moins courant que le traditionnel logback.xml, cette possibilité de configurer Logback par le code offre davantage de possibilités, ne serait-ce que par son caractère […]
Solution for : Cannot make a static reference to the non-static method
if you have this error that mean you are using your Repository interface in the place of you using and instance of it ,Exemple : if you have an interface PersonnelRepository and you want to use the function getOne(). if you do like that PersonnelRepository.getOne(id) you will have the error Cannot make a static reference […]
Solution for : How to join and split byte arrays, byte[] in JAVA
join and split byte arrays byte[] ? In this example, we will show you how to join and split byte arrays with ByteBuffer and System.arraycopy. ByteBuffer System.arraycopy 1. Join Byte Arrays This Java example uses ByteBuffer or System.arraycopy to join or concatenate two byte arrays. JoinByteArrayExample.java Output Terminal : 2. Split Byte Array In Java, […]
How to generate a random 12 bytes in Java ?
In Java, we can use SecureRandom.nextBytes(byte[] bytes) to generate a user-specified number of random bytes. This SecureRandom is a cryptographically secure random number generator (RNG). 1. Random 12 bytes (96 bits) 1.1 Generates a random 12 bytes (96 bits) nonce. HelloCryptoApp.java : Output : 1.2 Generates a random 20 bytes (160 bits) Output : 2. […]
Solution for : How to generate serialVersionUID using Intellij IDEA
generate serialVersionUID using Intellij IDEA : In IntelliJ IDEA, we need to enable this auto-generate serialVersionUID option manually. P.S Tested with IntelliJ IDEA 2019.3.4, it should work the same in other versions. Intellij IDEA Settings File -> Settings -> Editor -> Inspections -> Java -> Serialization issues: Find serialization class without serialVersionUID and check it. […]
Solution for : How to convert an InputStream into a String in Java ?
Problem : If you have a java.io.InputStream object, how should you process that object and produce a String ? We suppose that we have an InputStream that contains text data, and we want to convert it to a String, so for example we can write that to a log file. What is the easiest way […]
Solution for : Subtracting these two times (in 1927) giving a strange result ?
Problem : if you run the following program, which parses two date strings referencing times 1 second apart and compares them : The output is : Why is ld4-ld3 not 1 (as I would expect from the one-second difference in the times), but 353 ? If you change the dates to times 1 second later […]
How to avoid NullPointerException without != null statements
we always use object != null a lot to avoid NullPointerException on java. Is there a good alternative to this ? For example we often use : This checks for a NullPointerException for the obj object in the above snippet. Solution : This to me sounds like a reasonably common problem that junior to intermediate […]