Classes and Objects: A Deeper Look - Java: How to Program Early Objects - page 354

Section 8.10 Garbage Collection
• The Java Virtual Machine (JVM) performs automatic garbage collection (p. 338) to reclaim the
memory occupied by objects that are no longer in use. When there are no more references to an
object, the object is eligible for garbage collection. The memory for such an object can be re-
claimed when the JVM executes its garbage collector.
Section 8.11 static Class Members
•A static variable (p. 338) represents classwide information that's shared among the class's objects.
• static variables have class scope. A class's public static members can be accessed through a ref-
erence to any object of the class, or they can be accessed by qualifying the member name with
the class name and a dot ( . ). Client code can access a class's private static class members only
through methods of the class.
• static class members exist as soon as the class is loaded into memory.
•A method declared static cannot access a class's instance variables and instance methods, be-
cause a static method can be called even when no objects of the class have been instantiated.
•The this reference cannot be used in a static method.
Section 8.12 static Import
•A static import declaration (p. 342) enables you to refer to imported static members without
the class name and a dot ( . ). A single static import declaration imports one static member,
and a static import on demand imports all static members of a class.
Section 8.13 final Instance Variables
• In the context of an app's code, the principle of least privilege (p. 343) states that code should be
granted only the amount of privilege and access that it needs to accomplish its designated task.
•Keyword final specifies that a variable is not modifiable. Such variables must be initialized when
they're declared or by each of a class's constructors.
Section 8.14 Package Access
• If no access modifier is specified for a method or variable when it's declared in a class, the method
or variable is considered to have package access (p. 344).
Section 8.15 Using BigDecimal for Precise Monetary Calculations
• Any application that requires precise floating-point calculations without rounding errors—such as
those in financial applications—should instead use class BigDecimal (package java.math ; p. 346).
• BigDecimal static method valueOf (p. 347) with a double argument returns a BigDecimal that
represents the exact value specified.
• BigDecimal method add (p. 347) adds its argument BigDecimal to the BigDecimal on which the
method is called and returns the result.
• BigDecimal provides the constants ONE ( 1 ), ZERO ( 0 ) and TEN ( 10 ).
• BigDecimal method pow (p. 347) raises its first argument to the power specified in its second ar-
gument.
• BigDecimal method multiply (p. 347) multiplies its argument BigDecimal with the BigDecimal
on which the method is called and returns the result.
• Class NumberFormat (package java.text; p. 347) provides capabilities for formatting numeric
values as locale-specific String s. The class's static method getCurrencyInstance returns a pre-
configured NumberFormat for local-specific currency values. NumberFormat method format per-
forms the formatting.