Programacion java

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Part I
The Programmer’s Exam

1 2 3 4 5 Language Fundamentals Declarations and Access Control Operators and Assignments Flow Control, Exceptions, and Assertions Object Orientation, Overloading and Overriding, Constructors, and Return Types 7 8 9 6 Java.lang—The Math Class, Strings, and Wrappers Objects and Collections Inner Classes Threads

Language Fundamentals

• • • •

Java Programming Language Keywords Literals and Ranges of All Primitive Data Types Array Declaration, Construction, and Initialization Using a Variable or Array Element That Is Uninitialized and Unassigned Command-Line Arguments to Main Two-Minute Drill

Q&A Self Test


Chapter 1: Language Fundamentals

his chapter looks at the Java fundamentals thatyou need to pass the Java 1.4 Programmer exam. Because you’re planning on becoming Sun certified, we assume you already know the basics of Java, so this chapter concentrates just on the details you’ll need for the exam. If you’re completely new to Java, this chapter (and the rest of the book) will be confusing, despite our spectacularly cogent writing. That’s our story and we’re sticking to it!T


Java Programming Language Keywords (Exam Objective 4.4)
Identify all Java programming language keywords and correctly constructed identifiers. Keywords are special reserved words in Java that you cannot use as identifiers (names) for classes, methods, or variables. They have meaning to the compiler; it uses them to figure out what your source code is trying to do.Table 1-1 contains all 49 of the reserved keywords. You must memorize these for the test; you can count on being asked to select the keywords (and nonkeywords) from a list. Notice none of the reserved words have

Complete List of Java Keywords

abstract char double for int private strictfp throws assert

boolean class else goto interface protected super transient

break constextends if long public switch try

byte continue final implements native return synchronized void

case default finally import new short this volatile

catch do float instanceof package static throw while

Java Programming Language Keywords (Exam Objective 4.4)


capital letters; this is a good first step when weeding out nonkeywords on the exam. You’re probably familiar with most ofthem, but we’ll review them anyway. Don’t worry right now about what each keyword means or does; we’ll cover most of them in more detail in later chapters.
Look for questions that include reserved words from languages other than Java. You might see include, overload, unsigned, virtual, friend, and the like. Besides appearing in questions specifically asking for keyword identification, the“imposter” words may show up in code examples used anywhere in the exam. Repeat after me, “Java is not C++.”

Access Modifiers
The following are access modifiers:
■ private

Makes a method or a variable accessible only from within its

own class.
■ protected ■ public

Makes a method or a variable accessible only to classes in the same package or subclasses of the class. Makes a class, method,or variable accessible from any other class.

Class, Method, and Variable Modifiers
The following are class, method, and/or variable modifiers:
■ abstract ■ class ■ final

Used to declare a class that cannot be instantiated, or a method that must be implemented by a nonabstract subclass. Keyword used to specify a class. Used to indicate the superclass that a subclass is extending.


Makes it impossible to extend a class, override a method, or reinitialize a variable. Used to indicate the interfaces that a class will implement. Keyword used to specify an interface.

■ implements ■ interface ■ native

Indicates a method is written in a platform-dependent language,

such as C.
■ new

Used to instantiate an object by invoking the constructor.


Chapter 1:...
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