Java declare variable as public

How to declare a public variable in java

static fields can be accessed by referencing the class itself (e.g. stock.fruit), while for non-static fields you’ll need to reference an object that is an instance of the class holding the field. Edit: This only applies to public classes.

Public variable in java?

This code will not compile. You need to put these variables inside a class like so:

import java.util.Scanner; class stock < public static int fruit = 0; public static int ch; public static boolean demand = false; . 

If you want to access these variables outside, you can do this by referring to it like this: stock.fruit

If you want to use constants, you can declare an Interface, which you will then use to store constants as public static final

EDIT : You should not implement the interface, instead simply call it : InterfaceName.CONSTANT

It is also good practice to name your constants in all capital letter.

EDIT 2 : It seems that since java 5 (I Guess I'm really outdated. ) te use of static imports is considered better practice

Outside the Class definition you can't declare variables. Like the other guys said, you need to declare them inside the class.

If they are public and declared inside class Stock, you can access them from any other class. If they are friendly (no keyword, just static int fruit = 0;) you can access them from any class in the package. How to access them will depend on whether they're static or not. static fields can be accessed by referencing the class itself (e.g. stock.fruit), while for non-static fields you'll need to reference an object that is an instance of the class holding the field.

Now, with that said, I would very much recommend that you declare your variables where they should logically be placed, according to the context of the program. I'm not entirely sure what demand and ch are intended to mean, but just know that you can put them in any class, including Fruitmarket, so long as they have the correct access level modifiers (public, friendly, etc) and you attempt to access them in the right way (through the declaring class if they are static or through an instance of the declaring class if they are non-static)

Java Constant, The syntax to declare a constant is as follows: static final datatype identifier_name=value; static final datatype identifier_name=value; For example, price is a variable that we want to make constant. static final double PRICE=432.78; static final double PRICE=432.78; Where static and final are the non-access …

Declaring a public class in Java [duplicate]

Your class is called PastPresentFuture and I'm guessing by the error message that your file is not PastPresentFuture.java. you need to change it to be that so it matches the class name.

Edit: This only applies to public classes.

Javascript Public/Private Variables, return < //Public vars/methods a: a, That is also a one-of assignment of the value of a to an a property of the object that will be referenced by foo. Subsequent changes to the variable a will not affect the value of this property. changeVar: function < a = 2;

Public static final declaration of an instance variables in JAVA Interfaces

Use of uniform syntax in both classes and interfaces simplifies refactoring.

You may want to turn your interface into a class somewhere in future, or move these fields into a class, and you'll get a semantical difference if you overlook some fields defined without public static final (of course, we have tools for refactoring, but nonetheless).

I think it's the same thing as support of @Overriden annotation for implementations of methods declared in interfaces that was introduced in Java 6 - it's redundant in its current form, but may become useful in case of refactoring.

I don't think so. All interface variables are implicitly public static final so no meaning to mark them same.

Item 19: Use interfaces only to define types

When a class implements an interface, the interface serves as a type that can be used to refer to instances of the class. That a class implements an interface should therefore say something about what a client can do with instances of the class. It is inappropriate to define an interface for any other purpose.

One kind of interface that fails this test is the so-called constant interface. Such an interface contains no methods; it consists solely of static final fields, each exporting a constant. Classes using these constants implement the interface to avoid the need to qualify constant names with a class name. Here is an example:

// Constant interface antipattern - do not use! public interface PhysicalConstants < // Avogadro's number (1/mol) static final double AVOGADROS_NUMBER = 6.02214199e23; // Boltzmann constant (J/K) static final double BOLTZMANN_CONSTANT = 1.3806503e-23; // Mass of the electron (kg) static final double ELECTRON_MASS = 9.10938188e-31; >

The constant interface pattern is a poor use of interfaces. That a class uses some constants internally is an implementation detail. Implementing a constant interface causes this implementation detail to leak into the class’s exported API. It is of no consequence to the users of a class that the class implements a constant interface. In fact, it may even confuse them. Worse, it represents a commitment: if in a future release the class is modified so that it no longer needs to use the constants, it still must implement the interface to ensure binary compatibility. If a nonfinal class implements a constant interface, all of its subclasses will have their namespaces polluted by the constants in the interface.

There are several constant interfaces in the Java platform libraries, such as java.io.ObjectStreamConstants. These interfaces should be regarded as anomalies and should not be emulated.

If you want to export constants, there are several reasonable choices. If the constants are strongly tied to an existing class or interface, you should add them to the class or interface. For example, all of the boxed numerical primitive classes, such as Integer and Double, export MIN_VALUE and MAX_VALUE constants. If the constants are best viewed as members of an enumerated type, you should export them with an enum type (Item 30). Otherwise, you should export the constants with a noninstantiable utility class (Item 4). Here is a utility class version of the PhysicalConstants example above:

// Constant utility class package com.effectivejava.science; public class PhysicalConstants < private PhysicalConstants() < >// Prevents instantiation public static final double AVOGADROS_NUMBER = 6.02214199e23; public static final double BOLTZMANN_CONSTANT = 1.3806503e-23; public static final double ELECTRON_MASS = 9.10938188e-31; > 

Normally a utility class requires clients to qualify constant names with a class name, for example, PhysicalConstants.AVOGADROS_NUMBER. If you make heavy use of the constants exported by a utility class, you can avoid the need for qualifying the constants with the class name by making use of the static import facility, introduced in release 1.5:

// Use of static import to avoid qualifying constants import static com.effectivejava.science.PhysicalConstants.*; public class Test < double atoms(double mols) < return AVOGADROS_NUMBER * mols; >. // Many more uses of PhysicalConstants justify static import > 

In summary, interfaces should be used only to define types. They should not be used to export constants.

Rules For Variable Declaration in Java, Rules to Declare a Variable. A variable name can consist of Capital letters A-Z, lowercase letters a-z digits 0-9, and two special characters such as _ underscore and $ dollar sign. The first character must not be a digit. Blank spaces cannot be used in variable names. Java keywords cannot be used as variable …

Javascript Public/Private Variables

When you set the a key in the object you're returning, that's making a copy of the 'private' a variable.

You can either use a getter function:

return < //Public vars/methods a: function() < return a; >, changeVar: function () < a = 2; >>; 

Or you can use Javascript's built-in accessor functionality:

obj = < //Public vars/methods changeVar: function () < a = 2; >>; Object.defineProperty(obj, "a", < get: function() < return a; >>); return obj; 

Yes, if you're using a newer browser:

var foo = (function() < var a = 1; return < get a() < return a; >, changeVar: function () < a = 2; >> >)(); 

See a demo on JSFiddle.

There's also a more compatible method, but it requires changing the code that uses it:

var foo = (function() < var a = 1; return < getA: function() < return a; >, changeVar: function () < a = 2; >> >)(); alert(foo.getA()); // rather than foo.a 

If neither of these methods work for you, you'll have to either always assign both or always reference one (which must be the public one if you intend it to be public.

I normally use this pattern, that I haven't seen many do. I do this to avoid having to order my methods in any special way. If all is public , then one normally has to ensure that the methods called, are declared before the method call

var person = new Person("Mohamed", "Seifeddine"); person.getFullname(); person.getFirstname(); person.getLastname(); function Person(firstname, lastname) < var firstname, lastname; (function constructor()< setFirstname(firstname); setLastname(lastname) >)(); this.getFullname = getFullname; // Makes getFullName() public function getFullname() < // Will allow you to order method in whatever order you want. // If we where to have it as just this.getFullname = function () and same for firstname // as it is normally done, then this.getFirstname would have to be placed before this method. // A common pain in the ass, that you cannot order methods as you want! return getFirstname() + ", " + getLastname(); > this.getFirstname = getFirstname; function getFirstname() < return firstname; >function setFirstname(name) < firstname = name; >this.getLastname = getLastname; function getLastname() < return lastname; >function setLastname(name) < lastname = name; >> 

Declaring a public class in Java, This is only required for public classes, but it is good practice to name all files for the top level class it declares, public or otherwise (e.g. to help you find the source for a class).

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Java declare variable as public

Все члены класса в языке Java - поля и методы - имеют модификаторы доступа. В прошлых темах мы уже сталкивались с модификатором public . Модификаторы доступа позволяют задать допустимую область видимости для членов класса, то есть контекст, в котором можно употреблять данную переменную или метод.

В Java используются следующие модификаторы доступа:

• public : публичный, общедоступный класс или член класса. Поля и методы, объявленные с модификатором public, видны другим классам из текущего пакета и из внешних пакетов.
• private : закрытый класс или член класса, противоположность модификатору public. Закрытый класс или член класса доступен только из кода в том же классе.
• protected : такой класс или член класса доступен из любого места в текущем классе или пакете или в производных классах, даже если они находятся в других пакетах
• Модификатор по умолчанию . Отсутствие модификатора у поля или метода класса предполагает применение к нему модификатора по умолчанию. Такие поля или методы видны всем классам в текущем пакете.

Рассмотрим модификаторы доступа на примере следующей программы:

public class Program < public static void main(String[] args) < Person kate = new Person("Kate", 32, "Baker Street", "+12334567"); kate.displayName(); // норм, метод public kate.displayAge(); // норм, метод имеет модификатор по умолчанию kate.displayPhone(); // норм, метод protected //kate.displayAddress(); // ! Ошибка, метод private System.out.println(kate.name); // норм, модификатор по умолчанию System.out.println(kate.address); // норм, модификатор public System.out.println(kate.age); // норм, модификатор protected //System.out.println(kate.phone); // ! Ошибка, модификатор private >> class Person < String name; protected int age; public String address; private String phone; public Person(String name, int age, String address, String phone)< this.name = name; this.age = age; this.address = address; this.phone = phone; >public void displayName() < System.out.printf("Name: %s \n", name); >void displayAge() < System.out.printf("Age: %d \n", age); >private void displayAddress() < System.out.printf("Address: %s \n", address); >protected void displayPhone()< System.out.printf("Phone: %s \n", phone); >>

В данном случае оба класса расположены в одном пакете - пакете по умолчанию, поэтому в классе Program мы можем использовать все методы и переменные класса Person, которые имеют модификатор по умолчанию, public и protected. А поля и методы с модификатором private в классе Program не будут доступны.

Если бы класс Program располагался бы в другом пакете, то ему были бы доступны только поля и методы с модификатором public.

Модификатор доступа должен предшествовать остальной части определения переменной или метода.

Инкапсуляция

Казалось бы, почему бы не объявить все переменные и методы с модификатором public , чтобы они были доступны в любой точке программы вне зависимости от пакета или класса? Возьмем, например, поле age, которое представляет возраст. Если другой класс имеет прямой доступ к этому полю, то есть вероятность, что в процессе работы программы ему будет передано некорректное значение, например, отрицательное число. Подобное изменение данных не является желательным. Либо же мы хотим, чтобы некоторые данные были достуны напрямую, чтобы их можно было вывести на консоль или просто узнать их значение. В этой связи рекомендуется как можно больше ограничивать доступ к данным, чтобы защитить их от нежелательного доступа извне (как для получения значения, так и для его изменения). Использование различных модификаторов гарантирует, что данные не будут искажены или изменены не надлежащим образом. Подобное сокрытие данных внутри некоторой области видимости называется инкапсуляцией .

Так, как правило, вместо непосредственного применения полей используют методы доступа. Например:

public class Program < public static void main(String[] args) < Person kate = new Person("Kate", 30); System.out.println(kate.getAge()); // 30 kate.setAge(33); System.out.println(kate.getAge()); // 33 kate.setAge(123450); System.out.println(kate.getAge()); // 33 >> class Person < private String name; private int age = 1; public Person(String name, int age)< setName(name); setAge(age); >public String getName() < return this.name; >public void setName(String name) < this.name = name; >public int getAge() < return this.age; >public void setAge(int age) < if(age >0 && age < 110) this.age = age; >>

И затем вместо непосредственной работы с полями name и age в классе Person мы будем работать с методами, которые устанавливают и возвращают значения этих полей. Методы setName, setAge и наподобие еще называют мьютейтерами (mutator), так как они изменяют значения поля. А методы getName, getAge и наподобие называют аксессерами (accessor), так как с их помощью мы получаем значение поля.

Причем в эти методы мы можем вложить дополнительную логику. Например, в данном случае при изменении возраста производится проверка, насколько соответствует новое значение допустимому диапазону.

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