Java Static Keywords

6 Key excerpts on "Java Static Keywords"

• 

  eBook - PDF

  Java All-in-One For Dummies

  • Doug Lowe(Author)
  • 2023(Publication Date)
  • For Dummies

    (Publisher)

  You can create a static field, for example, and then assign values to it as a program executes. Thus, the value of the static field can change. To confuse things further, the word static can also mean interference, as in radio static that prevents you from hearing music clearly on the radio. But in Java, the term static doesn’t have anything to do with interference or bad reception. Chapter 3 IN THIS CHAPTER » Adding static fields to a class » Creating static methods » Creating classes that can be instantiated » Working with static initializers 274 BOOK 3 Object-Oriented Programming So what does the term static mean in Java? It’s used to describe a special type of field or method that isn’t associated with a particular instance of a class. Instead, static fields and methods are associated with the class itself, which means that you don’t have to create an instance of the class to access a static field or methods. Instead, you access a static field or method by specifying the class name, not a variable that references an object. The value of a static field is the same across all instances of the class. In other words, if a class has a static field named CompanyName, all objects created from the class will have the same value for CompanyName. Static fields and methods have many common uses. Here are but a few: » To provide constants or other values that aren’t related to class instances: A Billing class might have a constant named SALES_TAX_RATE that provides the sales tax rate. » To keep count of how many instances of a class have been created: A Ball class used in a game might have a static field that counts how many balls currently exist. This count doesn’t belong to any one instance of the Ball class. » In a business application, to keep track of a reference or serial number that’s assigned to each new object instance: An Invoice class might maintain a static field that holds the invoice number that is assigned to the next Invoice object created from the class.

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  eBook - PDF

  Programming Logic & Design, Comprehensive

  • Joyce Farrell(Author)
  • 2017(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  output Every student strives to be output a literate, responsible citizen. return When you write a class, you can indicate two types of methods: • Static methods , also called class methods , are those for which no object needs to exist, like the displayStudentMotto() method in Figure 10-18. Static methods do not receive a this reference as an implicit parameter. Typically, static methods include the word static in the method header, as shown shaded in Figure 10-18. (Java, C#, and C 11 use the keyword static . In Visual Basic, the keyword Shared is used in place of static .) • Nonstatic methods are methods that exist to be used with an object. These instance methods receive a this reference to a specific object. In most programming languages, you use the word static when you want to declare a static class member, but you do not use a special word when you want a class member to be nonstatic. In other words, methods in a class are nonstatic instance methods by default. 447 Understanding Static Methods Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 Using Objects A class is a complex data type defined by a programmer, but in many ways you can use its instances as you use items of simpler data types. For example, you can pass an object to a method, return an object from a method, or use arrays of objects. Consider the InventoryItem class in Figure 10-19. The class represents items that a company manufactures and holds in inventory. Each item has a number, description, and price. The class contains a get and set method for each of the three fields. In everyday language, the word static means “stationary”; it is the opposite of dynamic , which means “changing.” In other words, static methods are always the same for every instance of a class, whereas nonstatic methods act differently depending on the object used to call them.

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  eBook - PDF

  Concepts in Programming Languages

  • John C. Mitchell(Author)
  • 2002(Publication Date)
  • Cambridge University Press

    (Publisher)

  Also following C++, the Point class has public, private, and protected components. Although public , private , and protected are keywords of Java, these visibility speci-fications do not mean exactly the same thing in the two languages, as explained in Subsection 13.2.2 . Java terminology is slightly different from that of Simula, Smalltalk and C++. Here is a brief summary of the most important terms used to discuss Java: Class and object have essentially the same meaning as in other class-based object-oriented languages, field: data member Method: member function, static member : analogous to Smalltalk class field or class method, this: like C++ this or Smalltalk self , the identifier this in the body of a Java method refers to the object on which this method was invoked Native Method: method written in another language, such as C Package: set of classes in shared name space. We will look at several characteristics of classes and objects in Java, including static fields and methods, overloading, finalize methods, main methods, toString methods used to produce a print representation of an object, and the possibility of defining native methods. We will discuss the Java run-time representation of objects and the implementation of method lookup in Section 13.4 in connection with other aspects of the architecture of the run-time system. 390 Portability and Safety: Java Initialization. Java guarantees that a constructor is called whenever an object is created. Because some interesting issues arise with inheritance, this is discussed in Subsection 13.2.3 . Static Fields and Methods. Java static fields and methods are similar to Smalltalk class variables and class methods. If a field is declared to be static , then there is one field for the entire class, instead of one per object. If a method is declared static , the method may be called without using an object of the class. In particular, static methods may be called before any objects of the class are created.

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  eBook - PDF

  Elementary Synchronous Programming

  in C++ and Java via algorithms

  • Ali S. Janfada(Author)
  • 2019(Publication Date)
  • De Gruyter Oldenbourg

    (Publisher)

  Object-oriented programming (OOP) system | 77 Output: 5 200 100 All the files in the C++ standard library declare all of its entities within the std name- space. In fact, the statement using namespace std; requires the compiler to take anything which is in the std namespace and dump it in the global namespace. However, it increases the probability for name conflicts since a bunch of extra names, which were unexpected, were added to the global name-space, and that might butt the heads with some of your own names. Accordingly, it suffices to use the concerned identifiers using the :: operator in the programs which were involved with only a few identifiers in order to avoid this inconvenience. For instance, std::cout notifies the compiler that it requires the cout identifier which is in the std namespace. Therefore, the following two programs (both in the C++ codes) lead to the same outputs: Sample text . #include using namespace std; int main() { cout< int main() { std::cout<

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  No longer available |Learn more

  Learn Java 12 Programming

  A step-by-step guide to learning essential concepts in Java SE 10, 11, and 12

  • Nick Samoylov(Author)
  • 2019(Publication Date)
  • Packt Publishing

    (Publisher)

  By now, you should feel at home with most of the preceding keywords. By way of an exercise, you can go through the list and check how many of them you remember. We did not talk only about the following eight keywords:

  • const and goto are reserved but not used, so far
  • The assert keyword is used in an assert statement (we will talk about this in Chapter 4 , Exception Handling ).
  • The synchronized keyword is used in concurrent programming
    (we will talk about this in Chapter 8 , Multithreading and Concurrent Processing
    ).
  • The volatile keyword makes the value of a variable uncacheable.
  • The transient keyword makes the value of a variable not serializable
  • The strictfp keyword restricts floating-point calculation, making it the same result on every platform while performing operations in the floating-point variable
  • The native keyword declares a method implemented in platform-dependent code, such as C or C++

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  Restricted keywords

  The 10 restricted keywords in Java are as follows:

  • open
  • module
  • requires
  • transitive
  • exports
  • opens
  • to
  • uses
  • provides
  • with

  They are called restricted because they cannot be identifiers in the context of a module declaration, which we will not discuss in this book. In all other places, it is possible to use them as identifiers, for example:

  String to = "To";String with = "abc"; Although you can, this is a good practice not to use them as identifiers even outside module declaration.

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  Usage of the this and super keywords

  The this keyword provides a reference to the current object. The super keyword refers to the parent class object. These keywords allow us to refer to a variable or method that has the same name in the current context and in the parent object.

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  Usage of the this keyword

  Here is the most popular example:

  class A { private int count ; public void setCount (int count) { count = count; // 1 } public int getCount (){ return count ; // 2 }}

  The first line looks ambiguous, but, in fact, it is not: the local variable, int count , hides the private property instance

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  eBook - PDF

  Introduction to Computer Programming and Numerical Methods

  • Jocelyn O. Padallan(Author)
  • 2020(Publication Date)
  • Arcler Press

    (Publisher)

  A class can consists of any of the following types of variable. • Local variables: The local variables are the variables that are defined inside methods, constructors or blocks. The local variables are usually declared and initialized within the method and the variable will be destroyed when the method has completely executed. • Instance variables: The kind of variables that exist within a class but are present outside any method are known as the Instance variables. This type of variables is initialized when the class is instantiated. Instance variables can be accessed from inside any method, constructor or blocks of that particular class. • Class variables: The variables that are declared within a class, outside any method, along with the static keyword are known as Class variables. 3.5.2. Objects in Java Programming It is the fundamental unit of the Object-oriented Programming. The real-life Introduction to Computer Programming and Numerical Methods 82 entities are denoted by the objects. A typical Java program creates many objects which interact with the help of invoking methods. An object contains: State: Attributes of an object represent the state. The state depicts the properties of an object. Behavior: The behavior explains the methods of an object. Also, it depicts the response of an object with other objects. Identity: Identity makes the object unique while enabling one object to interact with the other objects. Example of an object: dog Table 3.1. Difference between Class and Objects in Java Object Class Object is defined as an instance of a class. Class is defined as a blueprint or tem -plate from which objects are created. Object is considered as a real-world entity like laptop, bed, mouse, chair, pen, mobile, keyboard, etc. Class is defined as a group of similar objects. Object is a physical entity.

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