CSC 243 Chapter 1, Spring 2015

Copyright © 2014 Pearson Education, Inc. Chapter 1 Introduction Java Software Solutions Foundations of Program Design John Lewis William Loftus Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2014 Pearson Education, Inc. Hardware and Software • Hardware – the physical, tangible parts of a computer – keyboard, monitor, disks, wires, chips, etc. • Software – programs and data – a program is a series of instructions • A computer requires both hardware and software • Each is essentially useless without the other Copyright © 2014 Pearson Education, Inc. CPU and Main Memory Central Central Central Central Processing Processing Processing Processing Unit Unit Unit Unit Main Main Main Main Memory Memory Memory Memory Chip that executes Chip that executes Chip that executes Chip that executes program commands program commands program commands program commands Primary storage area Primary storage area Primary storage area Primary storage area for programs and data for programs and data for programs and data for programs and data that are in active use that are in active use that are in active use that are in active use Synonymous with RAM Synonymous with RAM Synonymous with RAM Synonymous with RAM Copyright © 2014 Pearson Education, Inc. Input / Output Devices Central Central Central Central Processing Processing Processing Processing Unit Unit Unit Unit Main Main Main Main Memory Memory Memory Memory Copyright © 2014 Pearson Education, Inc. Monitor screen Monitor screen Monitor screen Monitor screen Keyboard Keyboard Keyboard Keyboard Mouse Mouse Mouse Mouse Touch screen Touch screen Touch screen Touch screen I/O devices facilitate I/O devices facilitate I/O devices facilitate I/O devices facilitate user interaction user interaction user interaction user interaction Secondary Memory Devices Central Central Central Central Processing Processing Processing Processing Unit Unit Unit Unit Main Main Main Main Memory Memory Memory Memory Copyright © 2014 Pearson Education, Inc. Information is moved Information is moved Information is moved Information is moved between main and between main and between main and between main and secondary memory secondary memory secondary memory secondary memory as needed as needed as needed as needed Hard Disk Hard Disk Hard Disk Hard Disk USB Flash Drive USB Flash Drive USB Flash Drive USB Flash Drive Secondary memory Secondary memory Secondary memory Secondary memory devices provide devices provide devices provide devices provide long long long long----term storage term storage term storage term storage Software Categories • Operating System – controls all machine activities – provides the user interface to the computer – manages resources such as the CPU and memory – Windows, Mac OS, Unix, Linux, • Application program – generic term for any other kind of software – word processors, games • Most operating systems and application programs have a graphical user interface (GUI) Copyright © 2014 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2014 Pearson Education, Inc. Java • The Java programming language was created by Sun Microsystems, Inc. • It was introduced in 1995 and it's popularity has grown quickly since • A programming language specifies the words and symbols that we can use to write a program • A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements Copyright © 2014 Pearson Education, Inc. Java Program Structure • In the Java programming language: – A program is made up of one or more classes – A class contains one or more methods – A method contains program statements • These terms will be explored in detail throughout the course • A Java application always contains a method called main • See Lincoln.java Copyright © 2014 Pearson Education, Inc. Copyright © 2014 Pearson Education, Inc. //******************************************************************** // Lincoln.java Author: Lewis/Loftus // // Demonstrates the basic structure of a Java application. //******************************************************************** public class Lincoln { //----------------------------------------------------------------- // Prints a presidential quote. //----------------------------------------------------------------- public static void main (String[] args) { System.out.println ("A quote by Abraham Lincoln:"); System.out.println ("Whatever you are, be a good one."); } } Copyright © 2014 Pearson Education, Inc. //******************************************************************** // Lincoln.java Author: Lewis/Loftus // // Demonstrates the basic structure of a Java application. //******************************************************************** public class Lincoln { //----------------------------------------------------------------- // Prints a presidential quote. //----------------------------------------------------------------- public static void main (String[] args) { System.out.println ("A quote by Abraham Lincoln:"); System.out.println ("Whatever you are, be a good one."); } } Output A quote by Abraham Lincoln: Whatever you are, be a good one. Java Program Structure public class MyProgram { } // comments about the class class header class header class header class header class body class body class body class body Comments can be placed almost anywhere Comments can be placed almost anywhere Comments can be placed almost anywhere Comments can be placed almost anywhere Copyright © 2014 Pearson Education, Inc. Java Program Structure public class MyProgram { } // comments about the class public static void main (String[] args) { } // comments about the method method header method header method header method header method body method body method body method body Copyright © 2014 Pearson Education, Inc. Comments • Comments should be included to explain the purpose of the program and describe processing steps • They do not affect how a program works • Java comments can take three forms: // this comment runs to the end of the line /* this comment runs to the terminating symbol, even across line breaks */ /** this is a javadoc comment */ Copyright © 2014 Pearson Education, Inc. Identifiers • Identifiers are the "words" in a program • A Java identifier can be made up of letters, digits, the underscore character ( _ ), and the dollar sign • Identifiers cannot begin with a digit • Java is case sensitive: Total, total, and TOTAL are different identifiers • By convention, programmers use different case styles for different types of identifiers, such as – title case for class names - Lincoln – upper case for constants - MAXIMUM Copyright © 2014 Pearson Education, Inc. Identifiers • Sometimes the programmer chooses the identifer(such as Lincoln) • Sometimes we are using another programmer's code, so we use the identifiers that he or she chose (such as println) • Often we use special identifiers called reserved words that already have a predefined meaning in the language • A reserved word cannot be used in any other way Copyright © 2014 Pearson Education, Inc. Reserved Words • The Java reserved words: abstract assert boolean break byte case catch char class const continue default do double else enum extends false final finally float for goto if implements import instanceof int interface long native new null package private protected public return short static strictfp super switch synchronized this throw throws transient true try void volatile while Copyright © 2014 Pearson Education, Inc. Quick Check Copyright © 2014 Pearson Education, Inc. Which of the following are valid Java identifiers? grade quizGrade NetworkConnection frame2 3rdTestScore MAXIMUM MIN_CAPACITY student# Shelves1&2 Quick Check Copyright © 2014 Pearson Education, Inc. Which of the following are valid Java identifiers? grade quizGrade NetworkConnection frame2 3rdTestScore MAXIMUM MIN_CAPACITY student# Shelves1&2 Valid Valid Valid Valid Invalid – cannot begin with a digit Valid Valid Invalid – cannot contain the '#' character Invalid – cannot contain the '&' character White Space • Spaces, blank lines, and tabs are called white space • White space is used to separate words and symbols in a program • Extra white space is ignored • A valid Java program can be formatted many ways • Programs should be formatted to enhance readability, using consistent indentation • See Lincoln2.java and Lincoln3.java Copyright © 2014 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2014 Pearson Education, Inc. Program Development • The mechanics of developing a program include several activities: – writing the program in a specific programming language (such as Java) – translating the program into a form that the computer can execute – investigating and fixing various types of errors that can occur • Software tools can be used to help with all parts of this process Copyright © 2014 Pearson Education, Inc. Language Levels • There are four programming language levels: – machine language – assembly language – high-level language – fourth-generation language • Each type of CPU has its own specific machine language • The other levels were created to make it easier for a human being to read and write programs Copyright © 2014 Pearson Education, Inc. Programming Languages • Each type of CPU executes only a particular machine language • A program must be translated into machine language before it can be executed • A compiler is a software tool which translates source code into a specific target language • Sometimes, that target language is the machine language for a particular CPU type • The Java approach is somewhat different Copyright © 2014 Pearson Education, Inc. Java Translation • The Java compiler translates Java source code into a special representation called bytecode • Java bytecode is not the machine language for any traditional CPU • Bytecode is executed by the Java Virtual Machine (JVM) • Therefore Java bytecode is not tied to any particular machine • Java is considered to be architecture-neutral Copyright © 2014 Pearson Education, Inc. Java Translation Copyright © 2014 Pearson Education, Inc. Development Environments • There are many programs that support the development of Java software, including: – Java Development Kit (JDK) – Eclipse – NetBeans – BlueJ – jGRASP • Though the details of these environments differ, the basic compilation and execution process is essentially the same Copyright © 2014 Pearson Education, Inc. Syntax and Semantics • The syntax rules of a language define how we can put together symbols, reserved words, and identifiers to make a valid program • The semantics of a program statement define what that statement means (its purpose or role in a program) • A program that is syntactically correct is not necessarily logically (semantically) correct • A program will always do what we tell it to do, not what we meant to tell it to do Copyright © 2014 Pearson Education, Inc. Errors • A program can have three types of errors • The compiler will find syntax errors and other basic problems (compile-time errors) – If compile-time errors exist, an executable version of the program is not created • A problem can occur during program execution, such as trying to divide by zero, which causes a program to terminate abnormally (run-time errors) • A program may run, but produce incorrect results, perhaps using an incorrect formula (logical errors) Copyright © 2014 Pearson Education, Inc. Basic Program Development errors? errors? Edit and Edit and Edit and Edit and save program save program save program save program Compile program Compile program Compile program Compile program Execute program and Execute program and Execute program and Execute program and evaluate results evaluate results evaluate results evaluate results Copyright © 2014 Pearson Education, Inc.