What is static final class in java

Difference Between static and final in Java

Key Difference – static vs final in Java

Each programming language has a specific syntax. The programmer should follow these syntaxes when writing programs. The keywords of programming languages have specific meanings according to the tasks. They are provided by the programming language and cannot be used for user-defined variables, methods, classes, etc. The static and final are two keywords in Java. This article discusses the difference between static and final in Java. The key difference between static and final in Java is that static is used to define the class member that can be used independently of any object of the class while final is used to declare a constant variable or a method that cannot be overridden or a class that cannot be inherited.

CONTENTS

What is static in Java?

A class consists of data members (attributes) and methods. In order to call the methods, there should be an object of that specific class. When a method is declared as static, it is not needed to create an object to call that method. The method can be called using the class name. Refer the below program.

Figure 01: Java Program with static variables and static Method

According to the above program, class A contains number variable and display method. Both are static members. Therefore, it is not necessary to create an object to access the number variable and display method. The programmer can directly write the class name to print the number and to call the method display. So, there is no need to instantiate an object. If the number variable and display method are non-static, then there should be an object of type A.

Figure 02: Use of static Block

The above program contains the static block and the main method. The static block is called when the class is loaded. Therefore, the statement in the static block executes before the statement in the main block. If there are many static blocks, they will execute in sequence.

What is final in Java?

In the program, there can be variables of various types. If there is a variable as int x=1; later in the program, that variable value can be changed to some other value. A variable that is declared as final and initialized with a value cannot be changed later in the program.

Figure 03: Program with final Variable and Inheritance

According to the above program, x is a final variable. It is assigned a value 5. It cannot be changed some other value because it is declared as final. Java supports Object-oriented programming (OOP). One pillar of OOP is a polymorphism. One type of polymorphism is overriding. Class A has the display method. The class B extends class A and it has its own display method. When creating an object of type B and calling the display method will print “B” as the output. The display method of class A is overridden by the display method of class B.

If the programmer what to avoid overriding a method, then he can use the final keyword for that method. If the display method in class A is final, the display method in B will give an error because that method cannot be overridden.

Figure 04: final keyword in the Method

Another pillar of OOP is inheritance. It helps to reuse the already existing code. The new class can extend from the existing class and use the data members and methods of the existing class. If it is required to stop inheriting a class, the programmer can use the keyword ‘final’. Refer the below program.

Figure 05: final keyword in the Class

According to the above program, class A is declared as final. When class B extends A, it gives an error because class A is declared as final. It cannot be inherited by other classes.

What is the Similarity Between static and final in Java?

What is the Difference Between static and final in Java?

static vs final in Java

Summary – static vs final in Java

This article discussed two keywords in Java such as static and final. The difference between static and final in Java is that static is used to define the class member that can be used independently of any object of the class while final is used to declare a constant variable or a method that cannot be overridden or a class that cannot be inherited.

Reference:

1.What is Static Keyword in Java | static method and static variable, Telusko Learnings, 6 Mar. 2015. Available here
2.7.16 How to use Static Block in Java Tutorial, Telusko Learnings, 30 Apr. 2015. Available here
3.8.13 How to use Final Keyword in Java | Method , class and variable, Telusko Learnings, 26 Feb. 2015. Available here

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About the Author: Lithmee

Lithmee Mandula is a BEng (Hons) graduate in Computer Systems Engineering. She is currently pursuing a Master’s Degree in Computer Science. Her areas of interests in writing and research include programming, data science, and computer systems.

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What is static final class in java

Вопрос глуппый но задам. Сборщик мусора не сходит сума при работе с immutable? Наример нам приходится в программе таскать ‘с собой’ масивы строк и паралельно в них менять значения. Это жесть какая нагрузка на железо.

 public static void main(String[] args)

Вывод: I love Java I love Java Честно говоря, не понимаю, что удивительного в этом коде? Код же выполняется сверху вниз. А тут четверть статьи этому посвятили) Я так понимаю, что если я в конце в коде напишу: System.out.println(str1);, то вывод будет: I love Java I love Python Или я что-то не так понял?

Ведьмаку заплатите – чеканной монетой, чеканной монетой, во-о-оу Ведьмаку заплатите, зачтется все это вам

Всё что я должен понять из этой статьи: final для класса — класс нельзя наследовать, final для метода — метод нельзя переопределять, final для переменной — нельзя изменять первое присвоенное значение (сразу присваивать не обязательно), имя пишется капсом, слова через нижний пробел. Объекты всех классов обёрток, StackTrace, а также классы, используемые для создания больших чисел BigInteger и BigDecimal неизменяемые. Таким образом, при создании или изменении строки, каждый раз создаётся новый объект. Кратко о String Pool: Строки, указанные в коде литералом, попадают в String Pool (другими словами «Кэш строк»). String Pool создан, чтобы не создавать каждый раз однотипные объекты. Рассмотрим создание двух строковых переменных, которые указаны в коде литералом (без new String).

 String test = "literal"; String test2 = "literal"; 

При создании первой переменной, будет создан объект строка и занесён в String Pool. При создании второй переменной, будет произведён поиск в String Pool. Если такая же строка будет найдена, ссылка на неё будет занесена во вторую переменную. В итоге будет две различных переменных, ссылающихся на один объект.

Мало примеров и в целом, недосказано. Под конец вскользь упомянут String Pool, а что это не объясняется. Статья озаглавлена какFinal & Co, а по факту пару примеров по строкам, ну, такое. Это называется собирались пироги печь, а по факту лепёшки лепим. В любом случае, конечно, спасибо за труд. Но, гораздо лучше про строки написано здесь: Строки в Java (class java.lang.String). Обработка строк в Java. Часть I: String, StringBuffer, StringBuilder (более детальная статья на Хабре).

Получается мы не можем создать поле какого нибудь класса не константой public static final String name = «Амиго»; обязательно только так? => public static final String CHARACTER_NAME = «Амиго»; или можно написать и так и так?

«В прошлых лекциях мы видели простой пример наследования: у нас был родительский класс Animal, и два класса-потомка — Cat и Dog» ?! А была лекция о наследовании?! Может быть я где-то пропустил, поделитесь ссылкой, пожалуйста 🙂

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Java static and final, what are they and how to use them

When I first started coding in Java I struggled to understand the differences between static and final , what were they or when to use them, so I decided to write a short summary for the newcomers. To the point! Let’s see how we can use them in our code.

The final keyword

Final variables

Final variables are intended to serve as constants, values that shouldn’t (and won’t) ever change:

 class Car  public final int numberOfWheels = 4; > 

 Car myCar = new Car(); myCar.numberOfWheels = 1; >>> The final field Car.numberOfWheels cannot be assigned 

Final methods

class Car  public final int getNumberOfWheels()  return 4; > > class Sedan extends Car  // This won't work because the method getWeight is final! @Override public double getNumberOfWheels()  return 3; > > 

This can be useful in cases that, as the one described, the result or the behavior of the method should not change when called from subclasses.

Final classes

final class Pear  private double weight; private String color; > // This won't work because the Pear class is final! class MagicalPear extends Pear  > 

The static keyword

In Java, static simply implies that the field or method is not going to change its value or behavior across all the instances of an object. In other words, that means that we can call it without instantiating the object we are using. So, if we define a CurrencyConverter:

class CurrencyConverter  public static String EUR = "€"; public static double convertDollarsToEuros(double amountInDollars)  double rate = 0.90; return amountInDollars * rate; > > 

System.out.println(CurrencyConverter.convertDollarsToEuros(5.43D)); CurrencyConverter converter = new CurrencyConverter(); System.out.print(converter.convertDollarsToEuros(5.43D)); >>> 4.887 >>> 4.887 

In the same way, we can call the static variable EUR without instantiating the object and, unlike final variables, we can even modify it. But that we can do it doesn’t mean that we should, as its considered bad practice to modify static variables. That’s why more often than not, static variables are also final:

public static final String EUR = "€" 

Hopefully, we now understand a little bit better the differences between those two keywords as well as when to use them. Suggestions and constructive criticism are always welcome!

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