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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  Recyclerview inside another Recyclerview using Firebase Android data

  I’m learning about android now, and putting into practice what I’m learning, but now I have a problem that I can not solve, or find exactly what I want My idea was to add a recyclerView in Vertical…

  java android android-fragment android-recyclerview

  asked 4 years, 8 months ago Alan Santana 1

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  69

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  Exception error when running my code in Java

  The following error appears when I choose the first three options I created in my code: Exception in thread "main" java.util.Unknownformatconversionexception: Conversion = '2' at…

  java eclipse

  asked 4 years, 7 months ago Mikael 25

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  Sum of 3 matrices in a new matrix

  I need a program that adds 3 matrices of Nxm size. The user should be able to set the size (Nxm) of the matrices. But I don’t know what’s wrong. Java int linha = i; int coluna = j; int[][] matriz =…

  java matrix

  asked 4 years, 7 months ago boltJu 63

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  248

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  ParseException error

  I have a problem about DATE. This giving error on line 58 about: Exception in thread "main" java.text.Parseexception: Unparseable date: "" at java.text.Dateformat.parse(Dateformat.java:366)…

  java

  asked 4 years, 7 months ago Pedro 77

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  123

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  Char Search in Object Arraylist

  I’m learning java in college and I’m having a hard time developing the logic to search an Arraylist. I want to know if there is a password registered by the type attribute, the passwords were…

  java

  asked 4 years, 7 months ago Santon 13

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  254

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  java.sql.Sqlexception: Column 'id' not found

  My code to search in the BD by id. The class is ContatoDao: //Pesquisa por id public Contato pesquisaId(int id) { String sql = "select nome from contatos where id = "+id; Contato contato = null; try…

  java mysql sql java-ee

  asked 4 years, 7 months ago user71255

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  184

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  How to access the name and address in the Customer Class, and access description and price in the Java Product Class, being in the Box Class?

  I tried to use the following commands: // Requesting the customer’s name name = input.toString(); purchase[i]. getCliente(). setNome(name); // Código do produto a ser comprado, que é o endereço da…

  java array string oop classes

  asked 4 years, 7 months ago Ewerton Melo 1

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  fill arraylist with arraylist attribute information of another class

  I have an Event class with an attribute arraylist<string>lista. I fill this attribute in a Telalista Jframe and use a evento.setLista("informaçao"); to add the textField string to the…

  java oop swing arraylist

  asked 4 years, 7 months ago joao 1

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  286

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  AXIOS SENDS 2 REQUESTS INSTEAD OF 1

  Summary : When I Make Backend Requests with Postman all goes well, but when I make requests with Front-End Reactjs Axios 2 requests come to the API, 1 without Token and the other with Token. I am in…

  java react http-request axios

  asked 4 years, 6 months ago Gustavo de Carvalho Reinaldi 9

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  120

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  Divisors of a number which variable to print

  I came across a problem with the splitters of a number and that also goes to other problems I made this code to print me number dividers from largest to smallest, but it is just printing one of the…

  java

  asked 4 years, 6 months ago Rui Simões 9

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  73

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  Android Studio stopped working after installing Flutter and this error infirmmation

  Good morning! I had Android Studio installed on my machine and after installing Flutter it stopped working. I uninstalled Flutter and even then Android Studio does not work and only presents this…

  javascript java android-studio flutter java-8

  asked 4 years, 6 months ago luciano.vtn120 1

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  40

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  Data conversion using Combobox

  Hello, I’m having trouble dealing with an error in my program. I have two combobox inside a registration panel. When executing already appears the list of products and customers, but the code field…

  java string netbeans type-conversion combobox

  asked 4 years, 5 months ago Vinicius Lira 1

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  113

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  Delete firebase user from database and authentication

  Good afternoon I am trying to do the method that deletes the user from the database and authentication, but it is not working. private void excluirDeslogar(){ final DialogProgress dialogProgress =…

  java android firebase

  asked 4 years, 5 months ago Deborah Fontoura 1

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  176

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  Generate standard bar code 2 of 5 interspersed in java

  Good morning, I’m trying to implement a barcode generator to generate the payment code for a billet collection type. Researching realized needed to be in pattern 2 of 5 interspersed, the way I did…

  java java-ee java-8

  asked 4 years, 5 months ago Felipe D. Santos 11

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  102

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  Is it possible to change the color of a jtable cell of type Boolean?

  I am trying to change the background color of certain Jtable cells, but when I change the color of a Boolean column it loses the format of a Checkbox and appears written "true" or "false". I want to…

  java checkbox jtable background

  asked 4 years, 5 months ago Pedro Afonso 119

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  166

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  How to create an Arraylist with constructor method with String

  Hello, I would like to know how I could add these variables within this Arraylist. The program says it is not possible to put String in Publication, I tried casting and did not give. Thanks in…

  java apache netbeans arraylist

  asked 4 years, 5 months ago Ancapistola 11

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  141

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  How to create a variable-sized array in Java?

  I am trying to perform an exercise in Java that creates an A vector and adds even and odd values in 2 vectors, B and C, respectively. However, I am required to declare the size of these vectors…

  java array

  asked 4 years, 5 months ago Matheus Cavalcante 13

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  91

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  How to get the result of another method in Java?

  How I take the result of method 2 and put together with Resultado.setText of Method 1? 1 public void CalcularIMC(View view) { //recuperar valores digitados String Didade =…

  java android-studio

  asked 4 years, 4 months ago jfs15 3

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  45

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  I cannot capture the message I send in my Exception Java Custom

  Everybody, good afternoon, everybody! I need a help, I am creating some java Apis and I created some custom exceptions, when I invoke the type exection I created: throw new…

  java

  asked 4 years, 4 months ago Joo Pereira de albuquer Junior 1

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  61

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  SQL code problem in the @Query java annotation

  I am trying to perform a command through Inner Join in an annotation @Query in Java, but an error occurs. The code usually works when performing an SQL query without using Inner Join. It follows the…

  java mysql spring-boot

  asked 4 years, 4 months ago Lucas Gato 11

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  19

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  Page does not return Managedbean

  I’ve seen several similar posts, but it didn’t help much. My problem is very simple. I have a form page that will record data and display in a table using Managedbean. But when I click to write, the…

  java jsf primefaces java-bean

  asked 4 years, 4 months ago Tguitarful 19

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  60

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  Game of Old Doubt

  I have the following method: void selecionarBloco() { while (blocoSelecionadoCorretamente == false) { System.out.print("Qual casa você irá marcar (" + jogador +"):"); int blocoSelecionado =…

  java

  asked 4 years, 3 months ago Davi Ribeiro 27

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  How do I display the names and notes of an array in java?

  I’m a beginner in Java and decided to create this exercise to test my knowledge, but I’m breaking my head to show the values of this Array. I want him to show the name of the student at the end of…

  java

  asked 4 years, 3 months ago Carlos Henrique 31

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  49

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  Java - Calculating the value of hours for the person responsible for an event

  I am building a project (I am a student) in which I need to create an event company. The system shall provide: the amount spent with the responsible; the total cost of lectures; the total amount…

  java arraylist

  asked 4 years, 3 months ago Pablo Luis Leite 1

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  54

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  Random class doubt in Java

  Guys I’m trying to create a system of numbers mega sena. Basically I have to have a client(id) that will generate 6 random numbers. public class Cliente implements Serializable { private static…

  java jpa

  asked 4 years, 3 months ago Breno Rusciolelli 1

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  Java programmed calculator code error

  The error message is this: it is not possible to find the symbol symbol: gettext method () location: txttela variable of type Jtextfield There are several errors, but it is the same. What I…

  java

  asked 4 years, 3 months ago antonio ferreira lopes 11

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  88

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  download is not performed via outputStream

  I am trying to download a file. CSV that I have saved. However the download does not appear to me when I click the button and no error code appears. How can I test to see how far the procedure is…

  java spring-mvc input-output inputstream

  asked 4 years, 3 months ago Willian Lima 281

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  41

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  Problems adding multiple elements to Arraylist

  I’m practicing java and I’m having trouble printing the results inside Arraylist. Only shows the last typed result. public class ArrayList { public static void main(String[] args) { Scanner teclado…

  java

  asked 4 years, 2 months ago Carlos Henrique 31

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  26

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  Problem to request via restTemplate

  Hello I am developing a . jar that consults the dollar’s quotation value, through the request for an endpoint provided by the central bank. When I request via Postman json comes correctly, but by…

  java api web-service rest

  asked 4 years, 2 months ago rlp master 3

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  51

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  Explain to a beginner the query "if(! found)" in the code

  I have an exercise that searches a number on a predetermined vector; and answers "was found and which vector position" or answers that "the number is not in the vector". I wanted the explanation of…

  java logic condition

  asked 4 years, 2 months ago Rafael 1

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  46

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  Problem with a Char vector in Java

  Good morning! I made a code to read a char that can be a number or a keyboard letter. It’s very simple and running, but I made an integer n for the size of the vector and put the for…

  java

  asked 4 years, 2 months ago Doug_Java 11

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  33

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  Token Authentication Micro-service Java

  I am separating my authentication service into microservices, but when I separate the token into a module, my authentication service always returns 401 and does not log any This is my config class…

  java spring spring-boot spring-security spring-jpa

  asked 4 years, 2 months ago Ricardo Vieira 1

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  70

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  Problem adding elements to the array

  I am trying to add elements inside the Array through a method, but at the end of the execution it repeats the last value inserted. I made a simple code just to show the error and try to avoid this…

  java

  asked 4 years, 2 months ago Carlos Henrique 31

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  38

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  Incorrect data output in the list

  Hello, the following method is not showing the data output correctly. At the end of the run it shows the name of the product and then the message "CPF not registered". Follows an image to facilitate…

  java

  asked 4 years, 2 months ago Carlos Henrique 31

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  56

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  Problem with Hibernate -JPA

  mar 04, 2021 5:12:57 PM org.hibernate.jpa.boot.internal.PersistenceXmlParser doResolve INFO: HHH000318: Could not find any META-INF/persistence.xml file in the classpath…

  java hibernate jpa maven

  asked 4 years, 1 month ago Gabriwl 3

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  51

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  Data input - Java

  At the time of data entry, I realized that when I put the product name and enter, there is always a loose line, the next question does not come on time, only after another enter. However, when I…

  java data-entry

  asked 4 years, 1 month ago Programmer man 1

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  85

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  Netbeans Java - Failed to execute Goal org.codehaus.mojo:exec-Maven-plugin:1.5.0:exec (default-cli) on project Sintetizee:

  When I try to run my Java file in Netbeans, this error appears Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.5.0:exec (default-cli) on project Sintetizee: Command execution failed.:…

  java maven netbeans

  asked 4 years, 1 month ago Mikael 25

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  50

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  Problem identifying triangle in Java

  Well, I’m still much new in the world of programming and I’m trying to make a simple code where it says whether the triangle is isosceles, scalene or equilateral depending on the measurement of the…

  java

  asked 4 years, 1 month ago Leonardo Vaz 1

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  282

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  Failed to run Goal org.springframework.boot:spring-boot-Maven-plugin:2.4.3:run (default-cli)

  I have the following error in developing an application using the following tools: When running mvn spring-boot:run, it shows the error Failed to execute Goal…

  java api

  asked 4 years, 1 month ago Matheus Gimpel 1

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  26

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  Help with method to add new item

  Good afternoon I have this sales screen: As you can see I selected a product, set the quantity and the values were set automatically. Now my idea is, to add a new item, with the same fields,…

  java mysql spring-boot maven framework

  asked 4 years, 1 month ago Desenvolvimento FJ Sistemas 3

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  35

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  Problem climbing springboot application with Tomcat

  Good afternoon to all I built a small spring application just for learning purposes and I’m trying to run it with Tomcat, I’ve tried everything and always get error 404. Would someone please explain…

  java

  asked 4 years, 1 month ago Fred 11

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  58

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  How to show Yes and No instead of 0 and 1 in java?

  I’m caught in this problem, I need to show Yes and No in the xhtml table instead of 0 and 1, the return type in get and set is Bigdecimal and the shapes I tried always end up breaking or not running…

  java html table

  asked 4 years, 1 month ago Paulo Oliveira 23

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  26

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  Build error: "Resource Leak" when using Scanner

  I cannot compile my code because the following error appears below: Exception in thread "main" java.util.Unknownformatconversionexception: Conversion = '0' at…

  java error-page

  asked 4 years, 1 month ago Rafaela Machado 9

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  40

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  Manual String Breaking in JAVA

  Gentlemen, I am trying to do a routine that receives a certain text and a word from the user, after checking if within the text there is a word equal to what was requested. My attempt was to…

  java comparison string-concatenation characters jtextarea

  asked 4 years, 1 month ago Gabriel Galdino 3

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  18

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  javac -classpath . (Debian 10 Buster)

  I’m using the Geany to do so. However, I was unable to compile the simple Hello World!. With some researches I found two reference links, being them: https://www.guj.com.br/t/ola-mundo/51431/13…

  java debian geany

  asked 4 years, 1 month ago user191477

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  36

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  How to get the x and y coordinates in a circle from an angle

  I’m trying to create an analog clock and my idea was the following one would get the angle corresponding to the hour and then discover the position x e y of that angle in a circle and draw a line…

  java mathematics canvas bitmap coordinates

  asked 4 years ago Fillipe 46

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  Oracle database data in combo box

  In a Java project, I am using Hibernete, and Java Sprint Boot, the combo box was created in the registration screen, where the registration of a person is made, where a combo box is presented, with…

  java hibernate spring-boot

  asked 4 years ago Guilherme Bilibio 1

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  42

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  How to fill null spaces in a java array?

  I need to store a person’s first and last name within a variable. I was able to separate String words within an array and take the first name (by index 0) - and now I would like to know how to get…

  java array java-8

  asked 4 years ago Abraão Paiva 1

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  46

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  Logical operators with different value

  nome_adc_1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { double percent = (estimatedFare*0.20); double soma = estimatedFare + percent; double subtrai =…

  java string operators

  asked 4 years ago brunomassoni 3

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  2

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  32

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  I cannot update my object using PUT

  Although I know very little about Spring because I am learning, I cannot save a recovered object, the error is when I pass the object personal Pository.save(personSalva) I came to see some examples,…

  java spring

  asked 4 years ago dayson rodrigues 9