Java Reference
In-Depth Information
• The primary purpose of public methods is to present to the class's clients a view of the services
the class provides. Clients need not be concerned with how the class accomplishes its tasks.
• A class's private variables and private methods (i.e., its implementation details) are not acces-
sible to its clients.
Section 8.4 Referring to the Current Object's Members with the this Reference
• An instance method of an object implicitly uses keyword this (p. 322) to refer to the object's
instance variables and other methods. Keyword this can also be used explicitly.
• The compiler produces a separate file with the .class extension for every compiled class.
• If a local variable has the same name as a class's field, the local variable shadows the field. You
can use the this reference in a method to refer to the shadowed field explicitly.
Section 8.5 Time Class Case Study: Overloaded Constructors
• Overloaded constructors enable objects of a class to be initialized in different ways. The compiler
differentiates overloaded constructors (p. 324) by their signatures.
• To call one constructor of a class from another of the same class, you can use the this keyword
followed by parentheses containing the constructor arguments. If used, such a constructor call
must appear as the first statement in the constructor's body.
Section 8.6 Default and No-Argument Constructors
• If no constructors are provided in a class, the compiler creates a default constructor.
• If a class declares constructors, the compiler will not create a default constructor. In this case, you
must declare a no-argument constructor (p. 327) if default initialization is required.
Section 8.7 Notes on Set and Get Methods
Set methods are commonly called mutator methods (p. 331) because they typically change a val-
ue. Get methods are commonly called accessor methods (p. 331) or query methods. A predicate
method (p. 332) tests whether a condition is true or false.
Section 8.8 Composition
• A class can have references to objects of other classes as members. This is called composition
(p. 332) and is sometimes referred to as a has-a relationship.
Section 8.9 enum Types
• All enum types (p. 335) are reference types. An enum type is declared with an enum declaration,
which is a comma-separated list of enum constants. The declaration may optionally include other
components of traditional classes, such as constructors, fields and methods.
enum constants are implicitly final , because they declare constants that should not be modified.
enum constants are implicitly static .
• Any attempt to create an object of an enum type with operator new results in a compilation error.
enum constants can be used anywhere constants can be used, such as in the case labels of switch
statements and to control enhanced for statements.
•Each enum constant in an enum declaration is optionally followed by arguments which are passed
to the enum constructor.
•For every enum , the compiler generates a static method called values (p. 336) that returns an
array of the enum 's constants in the order in which they were declared.
EnumSet static method range (p. 337) receives the first and last enum constants in a range and
returns an EnumSet that contains all the constants between these two constants, inclusive.
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