Posts by Math • 30,313 points
252 posts
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25
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answer24414
viewsA: What is Maven for?
Maven is a tool developed by Apache, it serves to manage dependencies and automate your builds. Already the pom.xml is the Maven configuration file. Managing the dependencies It is very common to…
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6
votes1
answer4346
viewsA: How to sort alphabetically and numerically the same list?
You are looking for the interface Comparator. This interface gives you the ability to sort a collection in countless different ways. Its advantage over the Comparable is that you do not need to…
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7
votes3
answers10773
viewsA: Is it possible to use Java pointers?
Everything in Java that is not primitive is an object, objects are referenced by reference variables, in a way very similar to C pointers++. That is, what you know as a C++ pointer is known as a…
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6
votes1
answer13295
viewsA: Send file directly to printer via CMD
You can copy the file to the printer port, like this: copy/b c:\\endereco\\do\\arquivo.ext com3: Assuming the printer is on the COM3 port. The /b serves to indicate that the contents of the file is…
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108
votes13
answers20263
viewsA: What makes a language to be considered low/high level?
The "level" in this context can be understood as the level of detail of the algorithm for it to perform a given task. Making an analogy, consider that you pronounced the following sentence to a…
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2
votes3
answers500
viewsA: How can I separate a string for example 36529874 from two to two without having any separation carcter for example 36.52.98.74
Since it is a String with a fixed size and the output should follow the same pattern, I suggest making it as simple as possible: public class ConverteIMEI { public static void main(String[] args) {…
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4
votes2
answers1169
viewsA: Doubt - setDefaultCloseOperation
You must override the method windowIconified(), it is invoked whenever the frame is minimized. According to the documentation: Invoked when a window is changed from a normal to a minimized state.…
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3
votes2
answers801
viewsA: Confirm form closure
whereas the segundo if it is a Jframe within the main Jframe, the right one would be: JFrame segundo = new JFrame(); segundo.setBounds(100, 100, 450, 300); // No método abaixo, diz que não é para…
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7
votes2
answers3987
viewsA: Double formatting in Java
You can use Decimalformat: double d = 1243123.1; DecimalFormat df = new DecimalFormat("###,###.00"); System.out.println(df.format(d)); Exit: 1.243.123,10 However Decimalformat uses the properties of…
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0
votes1
answer676
viewsA: How to maintain the layout of the components created by Windowbuilder in eclipse after compilation?
Add the following code inside your main(): try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Throwable e) { e.printStackTrace(); } For example leaving so: public…
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1
votes1
answer358
viewsA: Button does not appear in window
One button is on top of the other, because by creating them you have set the same position of them within your Jframe: btnEnviar.setBounds(210 ,110, 170, 70); ... btnLimpar.setBounds(210 ,110, 170,…
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3
votes2
answers60
viewsA: Innerclass object is created at what point?
An Innerclass is created when using the operator new to create an instance of it. For example: public class Principal { public static void main(String[] args) { System.out.println("Comando: new…
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2
votes4
answers172
viewsA: Rewriting vs Incremental Improvement?
The client doesn’t know what a rewrite is. You who have to make the decision and budget a price, then the customer will accept your price or not, what you are doing or failing to do does not matter…
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25
votes2
answers1393
viewsQ: When should I choose whether or not to use a pointer when creating an object?
In C++, I’m used to seeing objects being created through the operator new, which is when the object is referenced by a pointer, thus: MinhaClasse *mc1 = new MinhaClasse(); This form seems to me the…
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4
votes1
answer1150
viewsA: Create graphical interface using Miglayout
I would make a composition of Layouts, to fix the components in the footer would use Borderlayout and put a panel at PAGE_END. The panel PAGE_END would also be of the Borderlayout type, to fix the…
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6
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answer2086
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59
votes3
answers6039
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26
votes3
answers1450
viewsA: Remote control of an Android is technically possible?
That sounds more like a job for Mythbusters, but I’ll take my chances on an answer. About the video The video seems to me clearly a montage. It sure is. But until then nothing wrong with that.…
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3
votes1
answer527
viewsA: java.lang.Nullpointerexception in this code
As you can see in your stack trace: at PrimosCT.<init>(PrimosCT.java:16) the exception occurs on line 16 of its class PrimosCT, which is the line pp.getButton1().addActionListener(this);. The…
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2
votes1
answer331
viewsA: Insert component without using setBounds
To add a Jcombobox without having to define the Bounds just use a Layout Manager which does not require them to be defined. A modern and flexible Layout Manager is the Miglayout, it generates little…
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5
votes3
answers225
viewsA: Doubt about showing local network IP
You can turn the signposted byte to non-signposted so: ip[i] & 0xFFL; Example: import java.net.InetAddress; import java.net.UnknownHostException; public class IP { public static void…
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4
votes2
answers588
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0
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answer98
viewsA: Vaadin project error in "pom.xml"
There is no version 3.0.1 yet, by looking at central repository, I believe you want the version 3.0-alpha-1. Use addiction that way: <dependency> <groupId>javax.servlet</groupId>…
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4
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answer244
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4
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answer83
viewsA: How do I create a String template and whenever the user passes something different report the error?
I believe the easiest way to do this is by using Regex. For your case, use the standard "^[a-zA-Z]\\w+". An example code that uses Regex above: import java.util.regex.Matcher; import…
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4
votes3
answers369
viewsA: Stringbuffer.equals and String.equals difference in Java
They are different. Implementation of the method equals() in the String.java class: public boolean equals(Object anObject) { if (this == anObject) { return true; } if (anObject instanceof String) {…
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5
votes1
answer935
viewsA: Join two Arraylist
I thought, Instead of having two ArrayListYou only need one, which has the name of the teams. Then you make a permutation 1 to 1, eliminating the cases where the team would face each other, and…
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4
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answers2276
viewsA: Methods without parameters and with parameters
You hit almost everything, just missed the part of returning a value. A function has the following format: tipoDeRetorno nomeDoMetodo(tipoDoParametro valorDoParametro) { //se o tipoDeRetorno for…
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5
votes1
answer191
viewsA: Passing data from one txt to another txt
You have two objects referencing the same file, there are no technical problems in it, but the way it is in your code besides unnecessary led you to make a logical mistake because you try to write…
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15
votes3
answers13854
viewsA: Fill string with zeros on the left
You can use the Decimalformat class to format its output value. So: //coloque isso no final do seu método converteDecimalParaBinario DecimalFormat df = new DecimalFormat("0000"); return…
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5
votes1
answer2887
viewsA: How to make an algorithm to turn capital letters into lowercase letters?
Portugol has a function that treats this, is the function caracteres_minusculos. From the documentation (which is inside the software itself): Biblioteca Texto funcao cadeia…
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7
votes1
answer5228
viewsA: Difficulties with rounding using Bigdecimal
Bigdecimal is immutable, so when you call the method setScale() it does not change the variable value bd, he returns the rounded value, however as there is no variable receiving the return value it…
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5
votes3
answers88
viewsA: Problem receiving random integer values in array
Eclipse does not point out any errors because you are not facing a syntax problem, but a logic problem. Your code even runs, but is stopped during its execution due to the launch of an exception.…
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6
votes2
answers158
viewsA: Play framework problem with form
Change: form(Task.class); To: Form.form(Task.class); Or if you prefer, statically import Form methods like this: import static play.data.Form.*; And keep using the way you did.…
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21
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answer5399
viewsA: What types of collections and their differences in java?
What are the differences between them? First of all it is important to understand that Collection is a term that may be ambiguous, as there are: Collection (or collections in free translation): That…
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24
votes4
answers1788
viewsA: Are Getters and Setters mandatory or facilitators?
The way to make getters or setters is a norm or convention? It is a convention determined by the company itself that maintains the language, Oracle, as you can see in: Javabeans Standard The…
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19
votes1
answer1099
viewsA: What is the difference between Integer.valueOf() when using String or int parameters?
When you do Integer.valueOf(0422), thanks to the prefix 0 at the beginning of the number, the conversion will be made based on the value in the octal basis, and not on the decimal basis. Which is…
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3
votes2
answers1038
viewsA: Java Timestamp and Mysql Timestamp
Answering your question: what is the best way to get a timestamp in Java where you can always reset mileseconds? For cases: System.currentTimeMillis(), Calendar.getInstance(). getTimeInMillis(), new…
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26
votes1
answer4728
viewsQ: What is technical debt?
Technical debt is the sum of some types of backlog in your project that can prevent the evolution of your project. However, this concept is much more comprehensive than that, and I would like to…
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3
votes1
answer855
viewsA: Compare Local time Joda Time
Localtime only stores the time information, does not store information of the day, therefore, 20h will always be bigger than 6h. Use Datetime instead, and indicate the full date, with day, month,…
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2
votes1
answer75
viewsA: Exception occcured while finding Account via ID
You should remove simple quotes from your SQL query: PreparedStatement pStmt = conn.prepareStatement("'select first_name from accout where first_name like ?'"); Should stay: PreparedStatement pStmt…
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4
votes1
answer213
viewsA: Comparable and Arrays.Sort
I found three problems in your code, the first is in the Corridax1 class. When you do: while(p[i] != null && i<p.length){ You are likely to receive one ArrayIndexOutOfBoundsException,…
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17
votes2
answers1978
viewsA: How to use the Java scanner
The @Earendul answer already points out the correct reason why the error occurs, however there is another solution to what it proposes. Explaining the error in my own words, when you use the command…
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12
votes4
answers2869
viewsA: Is it recommended to use natural primary key?
I’d say it’s not recommended. 1. Not everyone has CPF How to do it with foreigners? And minors who do not already have CPF? In these cases they can not create account? 2. CPF generators Imagine that…
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7
votes3
answers407
viewsA: Generate setters only in class constructor or generate outside constructor
You may well provide no method Setter public for an attribute if you wish, what is not recommended is to leave the attribute as public, because if one day you decide to change it to private and…
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1
votes2
answers630
viewsA: Add days to a jDateChooser
If you have to use pre-java 8 native libraries you can do so: Calendar c1 = Calendar.getInstance(); //pega data e hora atual java.sql.Date data1 = new java.sql.Date(c1.getTimeInMillis());…
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1
votes1
answer588
viewsA: Jtable, add multi-lines[Cell span] +Format table
To hide the vertical lines of your table just use the method setShowVerticalLines() of your Jtable object passing the argument false. tabela.setShowVerticalLines(false); To show the header you must…
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votes1
answer680
viewsA: Swap application label outside Manifest.xml
Use the following command within some method within your class that extends the main Activity: this.setTitle("Novo título");
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8
votes2
answers7414
viewsA: Manipulating String in Java
You can use Regex. Example: public class TesteRegex { public static void main(String[] args) { String frase = "Várias palavras em uma só String.\n" + "Ignorando pontos; Ponto-e-vírgula; Traços. E…
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5
votes3
answers8755
viewsA: What is the best way to replace a character in a given String position?
There are three classes options to handle Strings: String, Stringbuffer and Stringbuilder. Is used: String: when you don’t want to modify the text too much; Stringbuilder when you want to make…