Part II: Writing Your Own Java Programs - Get a Free Blog

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x More free books @ www.BingEbook.com Beginning Programming with Java For Dummies, 2nd Edition Part II: Writing Your Own Java Programs......................45 Chapter 4: Exploring the Parts of a Program . . . . . . . . . . . . . . . . . . . . .47 Checking Out Java Code for the First Time ................................................47 Behold! A program!...............................................................................48 What the program’s lines say .............................................................49 The Elements in a Java Program ..................................................................49 Keywords...............................................................................................50 Identifiers that you or I can define.....................................................52 Identifiers with agreed upon meanings .............................................52 Literals ...................................................................................................53 Punctuation...........................................................................................54 Comments .............................................................................................56 Understanding a Simple Java Program........................................................57 What is a method?................................................................................57 The main method in a program..........................................................60 How you finally tell the computer to do something ........................61 The Java class.......................................................................................63 Chapter 5: Composing a Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65 A Program to Echo Keyboard Input.............................................................66 Typing and running a program ...........................................................68 How the EchoLine program works.....................................................70 Getting numbers, words, and other things .......................................72 Type two lines of code, and don’t look back ....................................74 Expecting the Unexpected ............................................................................74 Diagnosing a problem ..........................................................................76 What problem? I don’t see a problem................................................86 Chapter 6: Using the Building Blocks: Variables, Values, and Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89 Using Variables ...............................................................................................89 Using a variable ....................................................................................90 Understanding assignment statements .............................................92 To wrap or not to wrap? ......................................................................93 What Do All Those Zeros and Ones Mean?.................................................94 Types and declarations .......................................................................95 What’s the point?..................................................................................96 Reading Decimal Numbers from the Keyboard..........................................96 Though these be methods, yet there is madness in ’t.....................97 Methods and assignments ..................................................................99 Variations on a Theme...................................................................................99 Moving variables from place to place..............................................100 Combining variable declarations .....................................................101
More free books @ www.BingEbook.com Table of Contents Chapter 7: Numbers and Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103 Using Whole Numbers.................................................................................103 Reading whole numbers from the keyboard...................................105 What you read is what you get .........................................................106 Creating New Values by Applying Operators ...........................................108 Finding a remainder ...........................................................................108 The increment and decrement operators .......................................111 Assignment operators .......................................................................117 Size Matters ..................................................................................................118 Chapter 8: Numbers? Who Needs Numbers? . . . . . . . . . . . . . . . . . . . .121 Characters.....................................................................................................122 I digress . . . .........................................................................................123 One character only, please................................................................125 Variables and recycling......................................................................125 When not to reuse a variable............................................................127 Reading characters ............................................................................129 The boolean Type ........................................................................................131 Expressions and conditions..............................................................132 Comparing numbers; comparing characters..................................133 The Remaining Primitive Types .................................................................138 Part III: Controlling the Flow .....................................139 Chapter 9: Forks in the Road . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141 Making Decisions (Java if Statements)......................................................143 Looking carefully at if statements ....................................................143 A complete program ..........................................................................147 Indenting if statements in your code ...............................................150 Variations on the Theme .............................................................................150 . . . Or else what? ................................................................................151 Packing more stuff into an if statement...........................................153 Some handy import declarations.....................................................155 Chapter 10: Which Way Did He Go? . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 Forming Bigger and Better Conditions......................................................157 Combining conditions: An example .................................................159 When to initialize?..............................................................................161 More and more conditions................................................................162 Using boolean variables ....................................................................165 Mixing different logical operators together ....................................166 Using parentheses..............................................................................168 xi
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Page 5 and 6: About the Author More free books @
Page 7 and 8: Dedication More free books @ www.Bi
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Page 21 and 22: If you already know what computer p
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Page 51 and 52: In This Chapter Compiling and runn
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More free books @ www.BingEbook.com
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Chapter 4 Exploring the Parts of a
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you should avoid naming it Canada,
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Figure 4-3: A pair of curly braces
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Figure 4-5: The terminology describ
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Figure 4-6: Calling the System.out.
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In This Chapter Chapter 5 Composing
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Figure 5-1: What part of the word
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1. Launch JCreator. 2. From JCreato
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Figure 5-6: The computer substitute
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Also, the table’s story has a sur
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At first you may think this guy has
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Figure 5-8: A helpful error message
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Chapter 5: Composing a Program The
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Avoid the knee-jerk response. Some
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Chapter 5: Composing a Program One
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Figure 5-13: Whadaya mean “NoSuch
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Spaces and indentation Java isn’t
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Chapter 6 Using the Building Blocks
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Figure 6-2: A variable (before and
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Figure 6-4: Reading an assignment s
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Figure 6-6: An extreme close-up of
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Figure 6-7: Getting the value of a
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Methods and assignments Note how I
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You can’t drag statements outside
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In This Chapter Processing whole n
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eflected nicely in Java. In Listing
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Figure 7-4: How to make six kids ve
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Figure 7-5: Hey, bud! Got change fo
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Figure 7-7: Using preincrement. Mor
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To cram a double value into an int
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Look at the bold line of code in Fi
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Are you trying to decide between us
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Figure 7-13: Storing the digits 422
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Chapter 8 Numbers? Who Needs Number
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Figure 8-2: The action in Listing 8
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Figure 8-5: Stop those pots! The co
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I wish I could give you twelve simp
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To represent a lone character in th
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Figure 8-11: The Fahrenheit tempera
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Figure 8-13: The Fahrenheit variabl
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In This Chapter Chapter 9 Forks in
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Figure 9-3: An if statement and its
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Figure 9-4: The allknowing Java pro
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Randomness makes me dizzy When you
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Anyway, whether you’re skinning c
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Anyway, notice that the value of ra
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An elegant way to think about if st
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In This Chapter Chapter 10 Which Wa
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Figure 10-2: Admission prices for B
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Figure 10-4: The choices in Listing
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Figure 10-6: Running the code in Li
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Figure 10-8: A capital offense. Fig
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} } More free books @ www.BingEbook
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Listing 10-8: Proud Winners and Sor
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Chapter 11 How to Flick a Virtual S
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Figure 11-2: A fork with eleven pro
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Figure 11-4: How many days until th
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Figure 11-6: From your mind to the
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In This Chapter Chapter 12 Around a
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Figure 12-1: Momma needs a new pair
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Figure 12-4: Look! I rolled a seven
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Figure 12-5: You win sum; you lose
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Figure 12-8: An incorrect run. You
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If you’ve read this whole section
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Figure 12-11: Jumping into a loop.
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Figure 12-13: The strategy in Listi
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In This Chapter Chapter 13 Piles of
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218 Part III: Controlling the Flow
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Figure 15-5: A readable display of
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Figure 15-6: No! Don’t do it! Mor
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Figure 15-7: Here we go loop, do lo
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That’s why my writing a Java prog
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In general, a someEnumTypeName.valu
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Figure 15-10: Entering loops for th
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Figure 15-14: Traveling a second ti
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In This Chapter Using for loops to
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Listing 16-1 uses a for loop — a
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Figure 16-3: A few one-room reports
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Listing 16-3 has a big fat conditio
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guestsIn[6] = 0; On one weekday, bu
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In This Chapter Creating classes C
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Figure 17-2: The code in Listing 17
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The two programs (in Listings 17-1
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Listing 17-4: What It Means to Be a
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Figure 17-6: From one class come th
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Figure 17-7: A table of purchases.
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Chapter 18 Using Methods and Variab
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Putting String variables to good us
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To display a String value, you can
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Figure 18-4: This looks even worse.
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Figure 18-6: Viewing the String cla
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Combining and using data At this po
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Turning strings into numbers The co
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Figure 18-9: Do you have change for
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Packages and import declarations In
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That’s very nice! How about the S
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class Check { int number; double am
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Chapter 19 Creating New Java Method
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The last names in Figure 19-1 may s
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Figure 19-2: Two objects, each with
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Chapter 19: Creating New Java Metho
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} void fillWithData() { Random myRa
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} void display() { NumberFormat cur
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Figure 19-6: Passing a value to a m
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Figure 19-7: Cbj’s account and Br
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In This Chapter Swinging into acti
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Figure 20-1: What a nice window! Mo
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Figure 20-4: The frame in Listing 2
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Taking Action The previous section
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Figure 20-6: A brandnew frame. Figu
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In This Chapter Chapter 21 Ten Sets
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Chapter 22 Ten Useful Classes in th
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Math Do you have any numbers to cru
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• Symbols • && (and operator),
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• C • Calling addInterest Metho
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File➪Open Workspace (JCreator), 3
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errors, diagnosing errors. See also
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input file creating, 222-223 naming
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enum type, 176 Faulty Password Chec
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pack, 352 parentheses and, 328 pars
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method and, 328 parameters and, 336
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testing code, 222-224 troubleshooti
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static, 320-323 String class, 305-3
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