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Lecture Java methods: Object-oriented programming and data structures (2nd AP edition): Chapter 5 - Maria Litvin, Gary Litvin

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Chapter 5 - Java syntax and style. This is an important chapter because it explains and contrasts two related aspects of writing code in a high-level programming language: language syntax rules and good programming style.

Java Methods Object-Oriented Programming and Data Structures 2nd AP edition with GridWorld Maria Litvin ● Gary Litvin /** * Chapter */ Java Syntax and Style Copyright © 2011 by Maria Litvin, Gary Litvin, and Skylight Publishing All rights reserved Objectives: • Learn to distinguish the required Java syntax from the conventional style • Learn when to use comments and how to mark them • Review reserved words and standard names • Learn the proper style for naming classes, methods, and variables • Learn to space and indent blocks of code 5­2 Comments • Comments are notes in plain English inserted in the source code • Comments are used to:     document the program’s purpose, author, revision history, copyright notices, etc describe fields, constructors, and methods explain obscure or unusual places in the code temporarily “comment out” fragments of code 5­3 Formats for Comments • A “block” comment is placed between /* and */ marks: /* Exercise 5-2 for Java Methods Author: Miss Brace Date: 3/5/2015 Rev 1.0 */ • A single-line comment goes from // to the end of the line: weight *= 2.2046; // Convert to kilograms 5­4 Javadoc Comments • Used by the JDK’s special utility program javadoc to automatically generate documentation in HTML format from the source code • Should precede a class, a method, or a field • Can use special javadoc tags:   @param – describes a parameter of a method @return - describes the method’s return value 5­5 Javadoc Comments (cont’d) /** indicates a javadoc comment /** * * * * * */ Returns total sales from all vendors; sets totalSales to Can use HTML tags @return total amount of sales from all vendors Common style 5­6 Reserved Words • In Java a number of words are reserved for a special purpose • Reserved words use only lowercase letters • Reserved words include:     primitive data types: int, double, char, boolean, etc storage modifiers: public, private, static, final, etc control statements: if, else, switch, while, for, etc built-in constants: true, false, null • There are about 50 reserved words total 5­7 Programmer-Defined Names • In addition to reserved words, Java uses standard names for library packages and classes: String, Graphics, JFrame, JButton, java.awt, javax.swing • The programmer gives names to his or her classes, methods, fields, and variables 5­8 Names (cont’d) • Syntax: A name can include:    upper- and lowercase letters digits underscore characters • Syntax: A name cannot begin with a digit • Style: Names should be descriptive to improve readability 5­9 Names (cont’d) • Programmers follow strict style conventions • Style: names of classes begin with an uppercase letter, subsequent words are capitalized: public class ActorWorld • Style: names of methods, fields, and variables begin with a lowercase letter, subsequent words are capitalized: private int sideLength; public void moveTo() 5­10 Names (cont’d) • Method names often sound like verbs: setBackground, getText, moveForward, stop • Field names often sound like nouns: color, steps, button, controlPanel • Constants often use all caps: PI, PIXELS_PER_INCH • It is OK to use short names for temporary “throwaway” variables: i, k, x, y, str 5­11 Syntax vs Style • Syntax is part of the language The compiler checks it • Style is a convention widely adopted by software professionals • The main purpose of style is to improve the readability of programs 5­12 Syntax • The compiler catches syntax errors and generates error messages • Text in comments and literal strings within double quotes are excluded from syntax checking • Before compiling, carefully read your code a couple of times to check for syntax and logic errors 5­13 Syntax (cont’d) • Pay attention to and check for:    matching braces { }, parentheses ( ), and brackets [ ] missing or extraneous semicolons correct symbols for operators +, -, =,

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