Most voted "java" questions
Use this tag when the question refers to some resource, information, or problem relating exclusively to the Java programming language. Java is a class-based, statically typed, reflective, and execution environment (JRE) language. Java programs are compiled to bytecode and run on a virtual machine (JVM), allowing a "write Once, run Anywhere" philosophy (WORA).
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answers6070
viewsConvert Jtextfield to integer and save to bd
I have a JTextField which is populated from the database as text, would like to save in another BD as int. Could someone please help me? My code: String sql = "INSERT INTO ass_cidade(id_cidade)…
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answer108
viewsProblem with programming logic in Java
Good afternoon to all, started two weeks ago a sequence of studies on programming for Android. I am studying by this book http://novatec.com.br/livros/googleand/sumario9788575221860.pdf bought it a…
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answer36
viewsMy button does not work when I put f:validateRegex
Without f:validateRegex the button works normally, but after you put f:validateRegex to validate the input data, it doesn’t work anymore, someone can help? Follow the code attached, I can’t format…
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answer38
viewsJava Mysql and FTP connection
My doubt is not about how to make a connection with ftp or mysql, because this is not getting. I connect using parameters such as host, port, user and password. My source code stores this…
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answers149
viewsCheck two denials in an if expression
I’m putting this on: if(!teste.trim().equals("") || (!(teste == null))){ // ...faz algo sem NullPointerException... } But the second clause is not working, the one that tests if it is not null. I…
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answer2816
viewsWhere can I find simple code examples made entirely in Java?
Where can I find simple code examples made entirely in Java? I need links!
javaasked 8 years, 3 months ago Danilo Silva 307 -
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answer650
viewsWhy does this method generate java.lang.Stackoverflowerror?
The following code generates this: java.lang.StackOverflowError at modelo.Secao.eleitores(Secao.java:67) And I don’t know why.…
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answers82
viewsfill as data an Array up to a specific value
I need to make a program that reads the keyboard names until the user type the word "order", and then print the typed names in the order they were typed. So far, I’ve tried to resolve this issue…
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answers210
viewsHow would I look regex to handle this case?
I’m not able to separate words this way: In case I have CPFConsole, wanted to separate to cpf and console. The code I have separates so: ([A-Z][a-z]+)|([a-z]{0,})|([A-Z]{2,}) But that code separates…
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answer183
viewsJava Trigger Return
I have a Rigger that checks if the user login has more than 3 characters and if it does not have it returns the msg "login must have more than 3 characters", how can I capture this return in java…
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answer56
viewsHow to change Padding or margin of homeasupindicator
How to take the space between arrow and icone android?…
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answer66
viewsRotation over a point on a 2D pivot in Java
I’m trying to figure out how to rotate a vector over a point (another vector) as a PIVOT tried on some websites that gave me the following code: public Vector2 rotate_point(float cx,float cy,float…
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answer524
viewsSort String List
Does anyone know how to sort a list (Array List)of Strings containing alphanumeric information of the type: "ABC 12" "A 8"
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answer133
viewsError: Exception in thread "main" - Stackoverflowerror
I created a library CRUD, but when I installed the class Biblioteca in the main, and was running occurred this giant error: Class Cadastrar: package Operacoes; import…
javaasked 7 years, 5 months ago italo vinicius 59 -
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answer34
viewsEnterprise services in the cloud
The "breakthrough" of cloud services technology will lead to Webservices in the cloud rather than a private network of enterprise X or even local network?
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answer76
viewsObject null, I don’t understand why
I have this myDB object which is an object of the Databasehelper class, but when I try to invoke a method of that class it says that that object is null. Class where this object: public class…
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answer186
viewsNullpointerexception - Genetic Algorithm
package chapter2; public class AllOnesGA { public static void main(String[] args) { //Cria instância da classe "GeneticAlgorithm" GeneticAlgorithm ga = new GeneticAlgorithm(100, 0.01, 0.95, 0);…
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answer62
viewsJava "per unit" logic
How can it be a method to return the following: Knowing that 220 is equivalent to 0.3275 and that with each addition of 0.0049 in the value of 0.3275, it will increase in one unit the 220, or with…
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answer72
viewsCheck if the user has balance/credit
I am making an app in which I need to check if the person has credit on the mobile. I was wondering how can I do it. Mt thank you
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answer76
viewsCan someone give me a sense of how I do
Model computationally the representation of the functioning of a lamp, where it is possible to light, erase and check whether the lamp is access. I did this: class Lampada { boolean aceso = true;…
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answers464
viewsHow to get HTML code from a protected page with Cloudflare?
I’m trying to get the HTML of a page with the Jsoup. This page has Cloudflare as protection and, instead of getting the HTML code of the site I’m interested in, it’s returning me the HTML of the…
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answers286
viewsHow to avoid memory bursting with recursiveness
I have a function that is called recursively, how to avoid memory bursting ?? int cont = 0; public void recur() { recur(); cont ++; System.out.println("Chamado: " + cont); }…
javaasked 7 years, 1 month ago Lucas Caresia 2,663 -
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answer43
viewsProblem with do while
public static void main(String[] args) { Scanner sc = new Scanner(System.in); BancoConta p1 = new BancoConta(); p1.inicio(); } public void inicio() { do { System.out.println("Para criar conta…
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answers6416
viewsCheck if the string contains only numbers
How can I check if a string contains only numbers? For example, you can’t have * / = e etc... only numbers. Because I need to convert a string to int and if you type letters, symbols will generate…
javaasked 6 years, 11 months ago user92401 -
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answer356
viewsScroll between two dates
I have two dates in milliseconds. I need to recover every day of that period to make an insert in the database. I thought I’d do one for each day of that period, but I have no idea how to do it!…
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answer88
viewsmain(String[]) exceeds 65535 bytes limit
Hello. I need to execute the code below with values that exceed those allowed by the main string, what I do? It is a list of numbers exceeding 65535 characters. in reality the program will be used…
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answer157
viewscould not open terminal for stdout
I am having a problem with Gradle when executing any command is returned to me the following error message: * What went wrong: Could not open terminal for stdout: could not get termcap entry Preview…
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answer71
viewsGet Object id[]
I need to get the id of these objects. Object[] classe = getNames().toArray(); String[] strings = Arrays.stream(classe ).map(Object::toString). toArray(String[]::new); for (int…
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answers261
viewsHelp in Java: Arrays
Exercise: Make two lists of names in the form of arrays, compare how many names on List 1 are on List 2, and then calculate the percentage of these, about the percentage of total people on List 2.…
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answer1059
viewsError: Unable to locate or load Olamundo main class.java
I’m trying to compile and run a "hello world" in Java from the command line. My code is: public class OlaMundo{ public static void main(String[] args){ System.out.println("Oi , funcionou"); } } I’m…
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answers152
viewsWhen do I use.metodo(). metodo()?
Good night. I have one question: when I use a syntax like: metodo(). metodo()? When and how I use this method?
javaasked 6 years, 4 months ago Fernando Costa Leite 15 -
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answer178
viewsHow many classes can we have in one package?
How many classes can we have in a single package?…
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answer46
viewsIt is allowed to perform the operation module % with double number in java, and how to change a single position of a string in java?
My doubts.. It is allowed to perform the operation module % with floating point number in java, and why? Because in compilers like c++ this operation is not allowed. How do I access an element of a…
javaasked 6 years, 4 months ago Victor OCV 393 -
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answer151
viewsError testing Cielo sandbox
When accessing the urls https://apiquerysandbox.cieloecommerce.cielo.com.br/1/sales/{Paymentid} when replacing Paymentid with a value: 1 (random value) I get this message: "Message": "The requested…
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answer250
viewsUpdate system in Java Web
Good afternoon, everyone, I have the idea of making a system with Java Web, but I’m starting to learn java now. A friend told me about doing with Java Web and told me to do in Python. The arguments…
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answer54
viewsHow do I run my code asynchronously and in real time or with each given time span?
I need to know how to run this code on my server, asynchronously and in real time, or every 5 minutes, for example. String asB64 =…
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answer67
viewsjavax.naming.Noinitialcontextexception:
I am trying to do a university job with messageria, but my chat is not starting and presenting the following problem: javax.naming.NoInitialContextException: Cannot instantiate class:…
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answers366
viewsWhat’s wrong with my code? I’m a beginner
I want to create an employee class with the specifications below, but I cannot return the show data method and the method calculate salary. It gives compilation errors when calling the methods, I…
javaasked 8 years, 3 months ago Thiago Marques 77 -
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answer195
viewsCall a new screen using a button (Scene Builder, Javafx)
I created two screens, one main and one that I intend to call using a button, as it would be the appropriate method to call this secondary screen?
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answer200
viewsReserved word as variable name
I’m building a program that integrates an online store with another program that controls the physical stock of a store. Communication is done through HTTP requests that respond in JSON format. In…
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answer36
viewsis it advisable to make java programs just by creating new classes within a single eclipse project?
I started studying the Java language recently and I have a question, it is better to create a new project or always create a new class within a single project even if it is not about the related…
javaasked 5 years, 12 months ago MARCELOHENRIQUE 1 -
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answers1334
viewsWhat is the difference between Double and Double in java?
I was making a code and, by mistake, I put double and the IDE accepted, I always used with the D capital. What’s the difference between the two?
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answer128
viewsFailed to add Class objects to the Array List
I have the class below: package carcleo.com.radiosingular.classes; import android.util.Log; import android.widget.Toast; import com.google.gson.JsonArray; import org.json.JSONArray; import…
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answer57
viewsWhy is the image I painted on the canvas disappearing?
package Principal; import java.awt.Canvas; import java.awt.Color; import java.awt.Graphics; public class Desenho { public static void main(String[]…
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answer100
viewsNo Persistence Provider for Entitymanager named x
This my project does not recognize my Persistence Provider. It follows the same below. Your location plus dependencies: I’m calling the same through a very simple XHTML using a Managebean. Below…
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answer87
viewsJava Interactions
Good morning to all dear programmers. I’m recently starting the JAVA language, I wonder if it is possible to perform as in javascript user interactivity with the software. Like an Hover that blurs…
javaasked 5 years, 9 months ago Raul Cesar 86 -
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answers623
viewsPrint ranges of numbers with final 5
I’m trying to print the numbers from 0 to 200 that have only the number 5 as the last digit. package Exercícios; public class NumerosQueComeçamComAlgarimo5 { public static void main (String [] args)…
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answers252
viewsPower with For or While
I need a little help, how do I calculate the power using the for or while, I don’t want to use the Math.Pow function()
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answer66
viewsDOUBT OF INHERITANCE IN JAVA(SMALL)
You were hired to develop a system for a motorcycle workshop, cars and trucks. Your first task will be to build a set of classes for represent the vehicles that will be met in the workshop. having…
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answer87
viewsOCA Java 8 certification, does it exist in Portuguese? Where should I pay for the test and at what institution?
Good afternoon my comrades. I am interested in making the JAVA 8, OCA certification test, only I do not speak English, there is proof in Portuguese, if there is where I must pay and in which RJ…