Category: Scope of Pattern Variables
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Constants in Interfaces – Object-Oriented Programming
Constants in Interfaces A field declaration in an interface defines a named constant. Naming conventions recommend using uppercase letters, with multiple words in the name being separated by underscores. Such constants are considered to be public, static, and final. These modifiers are usually omitted from the declaration, but can be specified in any order. Such…
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Other Aspects of Record Classes – Object-Oriented Programming
Other Aspects of Record Classes Some other aspects of record classes are mentioned below, and are covered in detail elsewhere in the book. Implementing Interfaces Records can implement interfaces, which is no different from a normal class implementing interfaces. As a record class is implicitly final, it cannot extend other classes. The CD record class…
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Array Store Check – Object-Oriented Programming
Array Store Check An array reference exhibits polymorphic behavior like any other reference, subject to its location in the type hierarchy (p. 278). However, a runtime check is necessary when objects are inserted in an array, as illustrated below. The following assignment is valid, as a supertype reference (Stack[]) can refer to objects of its…
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Overloaded Method Resolution – Object-Oriented Programming
Overloaded Method Resolution In this subsection, we take a look at some aspects regarding overloaded method resolution—that is, how the compiler determines which overloaded method will be invoked by a given method call at runtime. Resolution of overloaded methods selects the most specific method for execution. One method is considered more specific than another method…
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Reference Casting and the instanceof Operator – Object-Oriented Programming
5.11 Reference Casting and the instanceof Operator In this section we explore type casting of references and the instanceof operator that can be used to perform either type comparison or pattern matching. The Cast Operator The basic form of the type cast expression for reference types has the following syntax: Click here to view code…
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The instanceof Type Comparison Operator – Object-Oriented Programming
The instanceof Type Comparison Operator The binary instanceof operator can be used for comparing types. It has the following syntax when used as a type comparison operator (note that the keyword is composed of lowercase letters only): Click here to view code image reference_expression instanceofdestination_type The instanceof type comparison operator returns true if the left-hand operand…
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The instanceof Type Comparison Operator 2 – Object-Oriented Programming
As we have seen, the instanceof type comparison operator effectively determines whether the reference value in the reference on the left-hand side refers to an object whose class is a subtype of the type specified on the right-hand side. At runtime, it is the type of the actual object denoted by the reference on the…
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Polymorphism 2 – Object-Oriented Programming
In the for(:) loop at (3) in Example 5.23, depending on the type of the object denoted by the loop variable drawable, the call to the draw() method will result in the draw() method of this object to be executed. The instanceof type comparison operator returns true if the reference specified as its left-hand operand…
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Enum Values in Exhaustive switch Expressions – Object-Oriented Programming
Enum Values in Exhaustive switch Expressions A switch expression is always exhaustive—that is, the cases defined in the switch expression must cover all values of the selector expression type or the code will not compile (§4.2, p. 160). The switch expression below at (1) is exhaustive, as all values of the enum type Day are…
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Record Class Basics 2 – Object-Oriented Programming
The compiler automatically generates the necessary declarations for a record class when it is declared according to the simplified syntax form, in particular, when the record body is empty. Fields being final means that once a final field is initialized, its value cannot be changed. However, if a field refers to a mutable object, this…