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Downloading classes in Java. Write-off of own class loader

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shizuka last edited by

I want to download the classes from the switch, my own, jar file, to the project.
Specifically where I want to use it. Multimodal application. I have three modules, like A.war B.war C.jar. Where A and B are parent modules for C. So that's what I'm gonna delete module C I want to load the classes out of it with my own class loader. How can that be realized?
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zymir

Like the commentaries said, there's a class. https://docs.oracle.com/javase/8/docs/api/java/net/URLClassLoader.html ♪

Designer accepts as a parameter mass URL addresses before jar files.

URL[] classLoaderUrls = new URL[]{new URL("./somestuf.jar")};
URLClassLoader urlClassLoader = new URLClassLoader(classLoaderUrls);

It's not comfortable working with this:

Class loading

Class<?> beanClass = urlClassLoader.loadClass("ex.coolStuf.Stuf");

Establishment of class object

Constructor<?> constructor = beanClass.getConstructor();
Object beanObj = constructor.newInstance();

Method issue

Method method = beanClass.getMethod("sayHello");
method.invoke(beanObj);

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Calulator ofchisel in Java and enum-class
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For example calculate Instead of printing the result, it may be returned to the trigger code (although both can be combined).public int calculate(Operation operation, int a, int b) { switch (operation) { case ADD : return a + b; ... } Then you can do that.int sum = calculator.calculate(Operation.ADD, 1, 2); System.out.println(sum); // теперь вычтем что-нибудь из полученного выше sum int dif = calculator.calculate(Operation.SUBSTRACT, sum, 2); System.out.println(dif);
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Find the same members of these columns in the mass and revoke if the columns are not removed. No compression and withdrawal of the final matrix
Software Programming • java • • meriah

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for (int i = 0; i < n; n++) { if (mass[i][p] == mass[i][q]) { mass[i][p] = 0; mass[i][q] = 0; } else { for (int c = 0; c < s; c++) { mass[i][с] = 0; } } } The problem is this piece, that's it. else - it will be implemented on the first unequal meaning, i.e. the columns always wake up. There's only a time-happiness left in it, a flag, whether a match was found, and that flag has already lifted the entire column after the cycle.System.out.println("Вы ввели неверное ... This is not the case, but after the erroneous report, the programme has failed to be implemented with an incorrect value. Probably need to add a return.
NETBEANS 8.2 error when uninstalling
Software Programming • java netbeans • • Alberto

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The mistake you're getting is a https://bugs.openjdk.java.net/browse/JDK-8178846 . Some bug data are as follows:Type: Bug Status:RESOLVED Priority: P4 Resolution: Incomplete Affects Version/s: 8u121 Fix Version/s: None DatesCreated: 2017-04-14 18:00 Updated: 2017-04-16 22:38 Resolved: 2017-04-16 22:37 In the detail of the bug you can see a message almost identical to yours:A DESCRIPTION OF THE PROBLEM : # # A fatal error has been detected by the Java Runtime Environment: # # EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x000000005e806adf, pid=9148, tid=0x0000000000001e28 # # JRE version: Java(TM) SE Runtime Environment (8.0_121-b13) (build 1.8.0_121-b13) # Java VM: Java HotSpot(TM) 64-Bit Server VM (25.121-b13 mixed mode windows-amd64 compressed oops) # Problematic frame: # C [msvcr100.dll+0x36adf] # # Failed to write core dump. Minidumps are not enabled by default on client versions of Windows # # If you would like to submit a bug report, please visit: # http://bugreport.java.com/bugreport/crash.jsp # The crash happened outside the Java Virtual Machine in native code. # See problematic frame for where to report the bug. And you can determine that the problem is here, in the file msvcr100.dll:# Problematic frame: # C [msvcr100.dll+0x36adf] # # Failed to write core dump. Minidumps are not enabled by default on client versions of Windows Although as indicated above, on the page the bug is marked as Status:RESOLVED But then he says:Resolution: Incomplete Which is a confusing thing. He says he's RESOLUTION but at the same time it says the resolution is Incomplete, which can mean that it is not completely controlled and may appear in some operating systems or different scenarios.As a possible solution. Make sure you have everything updated first: operating system, Java version and https://netbeans.org/downloads/ . Note that the bug has been partially solved 16-04-2017So you can't trust if you're trying to re-install a downloaded NetBeans version before that date.
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private List<Worker> workers = new ArrayList<>(); workers.add(new Worker(...)); Inside ArrayList The components will be automatically expanded, making this quite optimal, so when used ArrayList- You won't have to think about their original size.
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Hello the primitive character data is char and as you know the char it is only possible to use a single character 'a', 'b', 'c', the String class wraps up so to speak to the type of char dato and makes it possible for you to form strings "DeCaracters".Taking this into account the object is the variable you declare of the String class:String miObjetoCadena = new String(); String miObjetoCadena2=""; String miObjetoCadena3="Stack Over"; String miObjetoCadena4= new String ("Stack Over");
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Why do you have to write "Class:
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https://eel.is/c++draft/conv.func (i.e. non-residential) function as a function indicator, but such conversion of non-static member functions to member performance indicators is not permitted.So, to get an address not a static member's function, it's clearly necessary to ask an address with a narco operator. &♪It should also be borne in mind that the operator & https://eel.is/c++draft/expr.unary.op#3.1 not a static member function. Example:struct some { void foo(); void bar() { &foo;//ошибка - foo не квалифицированный идентификатор (unqualified-id) &some::foo;//ок - some::foo - квалифицированный идентификатор (qualified-id) } };
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The mistake you would be having on the current stage would be the following or similar:non-static variable this cannot be referenced from a static contextThe reason is because of the method main which is static, you try to create an instance of FraccionBut that class has not been declared static.The keyword static modifies the life cycle of a member or method belonging to a class. Declared static members or methods are created at the time the class is loaded. While a non-static method or member is created only when the class is called, for example, using new(). In short, it is said that the static members belong to the class itself while the non-static belong to the instance of the class.1.Since in Java, the method main, which is the entry point of a program, has to be defined as static (precisely to enter a program you do not need to create an instance of the class that contains main), on your stage, you cannot access from main to class Fraccion Because this is not static.Possible solutionsIn the subparagraph ShadowingWhere https://docs.oracle.com/javase/tutorial/java/javaOO/nested.html , puts an example on how to solve this problem. It consists of:Create from main an instance of class Ejercicio01Use that instance to create the class instance FraccionWith these two solvent steps the prohibition of accessing a non-static member directly from a static context.If you apply that solution, the code would remain:public static void main(String args[]) { Ejercicio01 mEjercicio01 = new Ejercicio01(); /* *Esto funciona también así: Fraccion frax = mEjercicio01.new Fraccion(); *pero por claridad conviene poner el nombre de la clase contenedora */ Ejercicio01.Fraccion frax = mEjercicio01.new Fraccion(); frax.imprimir(); } Another solution would be to declare class Fraction Like staticThen you could access it from mainBecause you'd be calling a static member from a static context.In the definition of the class static: public static class Fraccion { //clase Fraccion int numerador; int denominador; //... } And in the main There would be no problem doing this:public static void main(String args[]) { Fraccion frax = new Fraccion(); frax.imprimir(); } PD: Since it is an exercise, I will not enter into the discussion of whether it is appropriate or not. For this case, I recommend that you use documentation-based solutions and read the indications given in it.Notes@AaronDiguila https://stackoverflow.com/a/2559596/5587982 quite clearly with an example.
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First I wouldn't implement a calculator like you're doing. It would use two stacks for operands and one for operators and, manipulating these two stacks, would have the results more performative than "pair" strings to take operations. If you decide to continue to implement this model, in your clickResult, call this method, passing the entire string, similar to what you show on the display for the user. This code is available and has been cited https://stackoverflow.com/questions/3422673/evaluating-a-math-expression-given-in-string-form public static double eval(final String str) { return new Object() { int pos = -1, ch; void nextChar() { ch = (++pos < str.length()) ? str.charAt(pos) : -1; } boolean eat(int charToEat) { while (ch == ' ') nextChar(); if (ch == charToEat) { nextChar(); return true; } return false; } double parse() { nextChar(); double x = parseExpression(); if (pos < str.length()) throw new RuntimeException("Unexpected: " + (char)ch); return x; } // Grammar: // expression = term | expression `+` term | expression `-` term // term = factor | term `*` factor | term `/` factor // factor = `+` factor | `-` factor | `(` expression `)` // | number | functionName factor | factor `^` factor double parseExpression() { double x = parseTerm(); for (;;) { if (eat('+')) x += parseTerm(); // addition else if (eat('-')) x -= parseTerm(); // subtraction else return x; } } double parseTerm() { double x = parseFactor(); for (;;) { if (eat('*')) x *= parseFactor(); // multiplication else if (eat('/')) x /= parseFactor(); // division else return x; } } double parseFactor() { if (eat('+')) return parseFactor(); // unary plus if (eat('-')) return -parseFactor(); // unary minus double x; int startPos = this.pos; if (eat('(')) { // parentheses x = parseExpression(); eat(')'); } else if ((ch >= '0' && ch <= '9') || ch == '.') { // numbers while ((ch >= '0' && ch <= '9') || ch == '.') nextChar(); x = Double.parseDouble(str.substring(startPos, this.pos)); } else if (ch >= 'a' && ch <= 'z') { // functions while (ch >= 'a' && ch <= 'z') nextChar(); String func = str.substring(startPos, this.pos); x = parseFactor(); if (func.equals("sqrt")) x = Math.sqrt(x); else if (func.equals("sin")) x = Math.sin(Math.toRadians(x)); else if (func.equals("cos")) x = Math.cos(Math.toRadians(x)); else if (func.equals("tan")) x = Math.tan(Math.toRadians(x)); else throw new RuntimeException("Unknown function: " + func); } else { throw new RuntimeException("Unexpected: " + (char)ch); } if (eat('^')) x = Math.pow(x, parseFactor()); // exponentiation return x; } }.parse(); }
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Post-increment operator and pre-increment
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I reproduce the first iteration step by step:1.- for (int i = 0; i < 10;) {At this point you are assigned the value 0 a i.2.- i = i++;At this point i increase its value in 1 through i++, but as a "postincrement" is the value that is assigned to i is the one that had before increasing, the value is increased but the last thing that is executed is the assignment, the value of i as it was.That last one was not necessary, it could have been left as only i++without the assignment.3.- System.out.println("Hola Mundo");Write "Hello World."4.- System.out.println("i = " + i); // Muestra i = 0Here he writes "i = 0" because i It's never been increased as you expected.If you want me to start 1 You must do the increase value correctly:for (int i = 0; i < 10;) { i++; System.out.println("Hola Mundo"); System.out.println("i = " + i); // Muestra i = 0 }
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Java mass of function
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So you need to keep all the meanings y?If so, just reclassify y to a mass of size to the number of points, that is (in your case)double[] y = new double[(int)((2.8 - 0.2)/0.002)]; and an additional variable for the time. In the end, replace y by y[z++] = ...where z is the variable type int, which is pre-cycled and equal to zero.
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Software Programming • java 8 class • • Avante

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I think the chorecta way of a class enum is: NombreClase nombreObjeto = NombreClase.nombreObjetoEnum;. In this case it would be:TaxCalculationSettingTypes itemType = TaxCalculationSettingTypes.CONFIGURATION;
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A more didactic way to solve this is like this:public class Cliente implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String nome; private String email; private int numero1; private int numero2; private int numero3; private int numero4; private int numero5; private int numero6; public Cliente(int[] numeros){ int numero1 = numeros[0]; int numero2 = numeros[1]; int numero3 = numeros[2]; int numero4 = numeros[3]; int numero5 = numeros[4]; int numero6 = numeros[5]; } } public class Random1 { public static void main(String[] args) { Random gerador = new Random(); int[] valoresSorteados = new int[6]; for (int i = 0; i < 6; i++) { int valorRandom = gerador.nextInt(59); System.out.println(valorRandom); valoresSorteados[i] = valorRandom; } Cliente cliente = new Cliente(valoresSorteados); } } But it is worth noting the following, for a code of studies anything meets, in a truth project several problems with this implementation will appear, as for example trust that will come a 6-position array in the client class builder, so it is always good to try to follow the good practices of market code. If this is just to study object orientation I recommend you remove the part of the database to get easier, after you solve the logica problem you need is only save in the bank, go by parts
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Such packages are features of the internal implementation of JDK. The developers shall not use them because they may be modified without warning.All public interface packages are described in javadoc.
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How do you write ASCII figures on Java?
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A good idea would be to create a numerical class. It will contain a complete picture of the numbers, i.e. a set of lines, that if you put it on the screen, there'll be a picture of the numbers.If you want to use a monoshift, and the numbers have different widths, one solution may be to add a number of missing poles to the presentation, so the total width of all figures will be the same. Below is the code for monoshift as well as the function createDigits for the convenient creation of a set of figures from the description of the print. Please note that the description of the list should contain adding gaps, for example, between the figures. 1 and 2 Two layers of gaps, not one, because of its own width 1 per unit less than the width of all other figures.If you want to use a non-monoshire print, you need to write your own version of the function. createDigitswhich will search for gaps and create numerical facilities on the basis of them.static class Digit { String[] lines; public Digit(String... lines) { this.lines = lines; } /** * функция для удобного создания массива Digit[] из описания шрифта * работает только с моноширинными шрифтами, * причём моноширинность описания шрифта (то есть аргумента `lines`) должен гарантировать код, вызывающий функцию * * @param lines описание шрифта в виде строк с большими цифрами 0-9, цифры разделены пробелом * @return массив длины 10 */ public static Digit[] createDigits(String... lines) { int height = lines.length; int width = (lines[0].length() - 9 /* десять цифр => девять пробелов */) / 10; return IntStream .range(0, 10) // Stream из цифр 0-9 .mapToObj(digit -> new Digit(Stream .of(lines) // цифры в line идут следующим образом: // `width` символов цифры `0`, пробел, // `width` символов цифры `1`, пробел, // ... .map(line -> line.substring(digit * (width + 1), (digit + 1) * (width + 1) - 1)) .toArray(String[]::new)) ).toArray(Digit[]::new); } } public static void main(String[] args) { Digit[] digits = Digit.createDigits( " ### # ##### ##### # ####### ##### ####### ##### ##### ", " # # ## # # # # # # # # # # # # # # #", "# # # # # # # # # # # # # # #", "# # # ##### ##### # # ###### ###### # ##### ######", "# # # # # ####### # # # # # # #", " # # # # # # # # # # # # # # # #", " ### ##### ####### ##### # ##### ##### # ##### ##### " ); int height = digits[0].lines.length; // число 5781, для удобства уже разбитое на цифры int[] number = {5, 7, 8, 1}; for (int i = 0; i < height; i++) { for (int digit : number) { System.out.print(digits[digit].lines[i] + " "); } System.out.println(); } } Demonstration of work http://ideone.com/9QrPkH ♪
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Use a timer for a Java class method
Software Programming • java timestamp timer swagger • • Raziyah00

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You can test to perform a timer as follows:import java.text.*; import java.util.*; class Programa{ public static void main(String[] args) { long startTime = System.currentTimeMillis(); /* ... Principio del codigo que tardara en ejecutarse ... */ //Realizo una prueba de codigo que tarda 5 minutos en ejecutarse: try{ //5 minutos de duracion (En milisegundos): Thread.sleep(300000); }catch(Exception e){ System.out.println(e); } /* ... Fin del codigo que tardara en ejecutarse ... */ long endTime = System.currentTimeMillis(); long timeElapsed = endTime - startTime; float minutos = timeElapsed/(60*1000F); System.out.println("Tiempo de ejecucion en milisegundos: " + timeElapsed); System.out.println("Tiempo de ejecucion en minutos: " + minutos); //Si el programa tarda en ejecutarse 5 minutos o más: if(minutos>=5){ //Ejecuta lo siguiente: System.out.println("El programa dura cinco minutos o más"); }else{ //Si tarda menos de 5 minutos, ejecuta lo siguiente: System.out.println("El programa dura menos de cinco minutos"); } } } The result of execution by console would be something like this:Tiempo de ejecucion en milisegundos: 300000 Tiempo de ejecucion en minutos: 5.0 El programa dura cinco minutos o más

Downloading classes in Java. Write-off of own class loader

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