Chapter 1 Oracle

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BeginNew Tight Java A Beginner s Guide Fifth Edition Herb Schildt 632 7 Chapter 1. 2 Java A Beginner s Guide,Key Skills Concepts,Know the history and philosophy of Java. Understand Java s contribution to the Internet,Understand the importance of bytecode. Know the Java buzzwords, Understand the foundational principles of object oriented programming. Create compile and run a simple Java program,Use variables. Use the if and for control statements,Create blocks of code.
Understand how statements are positioned indented and terminated. Know the Java keywords,Understand the rules for Java identifiers. T he rise of the Internet and the World Wide Web fundamentally reshaped computing Prior. to the Web the cyber landscape was dominated by stand alone PCs Today nearly all. PCs are connected to the Internet The Internet itself was transformed originally offering. a convenient way to share files and information Today it is a vast distributed computing. universe With these changes came a new way to program Java. Java is the preeminent language of the Internet but it is more than that Java revolutionized. programming changing the way that we think about both the form and the function of a. program To be a professional programmer today implies the ability to program in Java it is. that important In the course of this book you will learn the skills needed to master it. The purpose of this chapter is to introduce you to Java including its history its design. philosophy and several of its most important features By far the hardest thing about learning. a programming language is the fact that no element exists in isolation Instead the components. of the language work in conjunction with each other This interrelatedness is especially. pronounced in Java In fact it is difficult to discuss one aspect of Java without involving. others To help overcome this problem this chapter provides a brief overview of several Java. features including the general form of a Java program some basic control structures and. operators It does not go into too many details but rather concentrates on the general concepts. common to any Java program,01 ch01 indd 2 7 20 11 3 04 32 PM. Chapter 1 BeginNew Tight Java A Beginner s Guide Fifth Edition Herb Schildt 632 7 Chapter 1. Chapter 1 Java Fundamentals 3,The Origins of Java, Computer language innovation is driven forward by two factors improvements in the art of. programming and changes in the computing environment Java is no exception Building upon. the rich legacy inherited from C and C Java adds refinements and features that reflect the. current state of the art in programming Responding to the rise of the online environment Java. offers features that streamline programming for a highly distributed architecture. Java was conceived by James Gosling Patrick Naughton Chris Warth Ed Frank and. Mike Sheridan at Sun Microsystems in 1991 This language was initially called Oak but. was renamed Java in 1995 Somewhat surprisingly the original impetus for Java was not the. Internet Instead the primary motivation was the need for a platform independent language that. could be used to create software to be embedded in various consumer electronic devices such as. toasters microwave ovens and remote controls As you can probably guess many different types. of CPUs are used as controllers The trouble was that at that time most computer languages. were designed to be compiled for a specific target For example consider C. Although it was possible to compile a C program for just about any type of CPU to do. so required a full C compiler targeted for that CPU The problem however is that compilers. are expensive and time consuming to create In an attempt to find a better solution Gosling and. others worked on a portable cross platform language that could produce code that would. run on a variety of CPUs under differing environments This effort ultimately led to the creation. About the time that the details of Java were being worked out a second and ultimately. more important factor emerged that would play a crucial role in the future of Java This. second force was of course the World Wide Web Had the Web not taken shape at about the. same time that Java was being implemented Java might have remained a useful but obscure. language for programming consumer electronics However with the emergence of the Web. Java was propelled to the forefront of computer language design because the Web too. demanded portable programs, Most programmers learn early in their careers that portable programs are as elusive as they. are desirable While the quest for a way to create efficient portable platform independent. programs is nearly as old as the discipline of programming itself it had taken a back seat to. other more pressing problems However with the advent of the Internet and the Web the old. problem of portability returned with a vengeance After all the Internet consists of a diverse. distributed universe populated with many types of computers operating systems and CPUs. What was once an irritating but a low priority problem had become a high profile. necessity By 1993 it became obvious to members of the Java design team that the problems of. portability frequently encountered when creating code for embedded controllers are also found. when attempting to create code for the Internet This realization caused the focus of Java to. switch from consumer electronics to Internet programming So while it was the desire for an. architecture neutral programming language that provided the initial spark it was the Internet. that ultimately led to Java s large scale success,01 ch01 indd 3 7 20 11 3 04 32 PM.
BeginNew Tight Java A Beginner s Guide Fifth Edition Herb Schildt 632 7 Chapter 1. 4 Java A Beginner s Guide,How Java Relates to C and C. Java is directly related to both C and C Java inherits its syntax from C Its object model. is adapted from C Java s relationship with C and C is important for several reasons. First many programmers are familiar with the C C syntax This makes it easy for a C C. programmer to learn Java and conversely for a Java programmer to learn C C. Second Java s designers did not reinvent the wheel Instead they further refined an. already highly successful programming paradigm The modern age of programming began. with C It moved to C and now to Java By inheriting and building upon that rich heritage. Java provides a powerful logically consistent programming environment that takes the best of. the past and adds new features required by the online environment Perhaps most important. because of their similarities C C and Java define a common conceptual framework for. the professional programmer Programmers do not face major rifts when switching from one. language to another, One of the central design philosophies of both C and C is that the programmer is in. charge Java also inherits this philosophy Except for those constraints imposed by the Internet. environment Java gives you the programmer full control If you program well your programs. reflect it If you program poorly your programs reflect that too Put differently Java is not. a language with training wheels It is a language for professional programmers. Java has one other attribute in common with C and C it was designed tested and refined by. real working programmers It is a language grounded in the needs and experiences of the people. who devised it There is no better way to produce a top flight professional programming language. Because of the similarities between Java and C especially their support for object. oriented programming it is tempting to think of Java as simply the Internet version of. C However to do so would be a mistake Java has significant practical and philosophical. differences Although Java was influenced by C it is not an enhanced version of C. For example it is neither upwardly nor downwardly compatible with C Of course the. similarities with C are significant and if you are a C programmer you will feel right at. home with Java Another point Java was not designed to replace C Java was designed to. solve a certain set of problems C was designed to solve a different set of problems They. will coexist for many years to come,How Java Relates to C. A few years after the creation of Java Microsoft developed the C language This is important. because C is closely related to Java In fact many of C s features directly parallel Java Both. Java and C share the same general C style syntax support distributed programming. and utilize the same object model There are of course differences between Java and C but. the overall look and feel of these languages is very similar This means that if you already. know C then learning Java will be especially easy Conversely if C is in your future then. your knowledge of Java will come in handy, Given the similarity between Java and C one might naturally ask Will C replace Java. The answer is No Java and C are optimized for two different types of computing environments. Just as C and Java will coexist for a long time to come so will C and Java. 01 ch01 indd 4 7 20 11 3 04 32 PM, Chapter 1 BeginNew Tight Java A Beginner s Guide Fifth Edition Herb Schildt 632 7 Chapter 1.
Chapter 1 Java Fundamentals 5,Java s Contribution to the Internet. The Internet helped catapult Java to the forefront of programming and Java in turn had a. profound effect on the Internet In addition to simplifying web programming in general Java. innovated a new type of networked program called the applet that changed the way the online. world thought about content Java also addressed some of the thorniest issues associated with. the Internet portability and security Let s look more closely at each of these. Java Applets, An applet is a special kind of Java program that is designed to be transmitted over the Internet. and automatically executed by a Java compatible web browser Furthermore an applet is. downloaded on demand without further interaction with the user If the user clicks a link. that contains an applet the applet will be automatically downloaded and run in the browser. Applets are intended to be small programs They are typically used to display data provided. by the server handle user input or provide simple functions such as a loan calculator that. execute locally rather than on the server In essence the applet allows some functionality to be. moved from the server to the client, The creation of the applet changed Internet programming because it expanded the universe. of objects that can move about freely in cyberspace In general there are two very broad. categories of objects that are transmitted between the server and the client passive information. and dynamic active programs For example when you read your e mail you are viewing. passive data Even when you download a program the program s code is still only passive. data until you execute it By contrast the applet is a dynamic self executing program Such a. program is an active agent on the client computer yet it is initiated by the server. As desirable as dynamic networked programs are they also present serious problems. in the areas of security and portability Obviously a program that downloads and executes. automatically on the client computer must be prevented from doing harm It must also be able to. run in a variety of different environments and under different operating systems As you will see. Java solved these problems in an effective and elegant way Let s look a bit more closely at each. As you are likely aware every time that you download a normal program you are taking. a risk because the code you are downloading might contain a virus Trojan horse or other. harmful code At the core of the problem is the fact that malicious code can cause its damage. because it has gained unauthorized access to system resources For example a virus program. might gather private information such as credit card numbers bank account balances and. passwords by searching the contents of your computer s local file system In order for Java to. enable applets to be safely downloaded and executed on the client computer it was necessary. to prevent an applet from launching such an attack. Java achieved this protection by confining an applet to the Java execution environment. and not allowing it access to other parts of the computer You will see how this is accomplished. shortly The ability to download applets with confidence that no harm will be done and that no. security will be breached is considered by many to be the single most innovative aspect of Java. 01 ch01 indd 5 7 20 11 3 04 32 PM, BeginNew Tight Java A Beginner s Guide Fifth Edition Herb Schildt 632 7 Chapter 1. 6 Java A Beginner s Guide,Portability, Portability is a major aspect of the Internet because there are many different types of.
computers and operating systems connected to it If a Java program were to be run on virtually. any computer connected to the Internet there needed to be some way to enable that program. to execute on different systems For example in the case of an applet the same applet must be. able to be downloaded and executed by the wide variety of different CPUs operating systems. and browsers connected to the Internet It is not practical to have different versions of the. applet for different computers The same code must work in all computers Therefore some. means of generating portable executable code was needed As you will soon see the same. a convenient way to share files and information Today it is a vast distributed computing universe With these changes came a new way to program Java Java is the preeminent language of the Internet but it is more than that Java revolutionized programming changing the way that we think about both the form and the function of a program To be a professional programmer today implies the

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