Java with BlueJ, 2016a

More documents

Recommendations

Info

46 CHAPTER 2. BASICS 2.5 The String Class It is very common for a program to work with text strings and the Java String class is provided to facilitate the many things that programmers need to do with text strings. String literals are written as a sequence of characters that are delimited by double quotes. For example: "this is a line of text" "my first name is Joe" "Joe was born on May 1, 1999" The assignment statement: String fullName = "Joe Smith"; declares fullName to be of type String. fullName is a variable and the Java compiler allocates memory for fullName. The memory location for fullName will contain a reference (an address) to the storage location where the text string ”Joe Smith” is actually stored. Memory for primitive types is handled differently. The memory location associated with a primitive type contains the value (not an address) of the variable. For example, an int variable will have a memory location reserved for it where the value of the variable is stored. There is a subtle difference that may be hard to appreciate at this time: a variable (of type String) holds a reference to the value instead of holding the actual value. The diagram below attempts to show the difference. Object References
2.5. THE STRING CLASS 47 Since text strings are objects of type String another way to declare fullName and assign it a value is to use the new operator: String fullName = new String("Joe Smith"); In general, the new operator is used to instantiate (to create) an object. Because text strings are so common Java provides the short cut for allocating a string, such as: String fullName = "Joe Smith"; new operator The only way to work with objects is through the methods that are defined in the class from which the object is instantiated. The String class provides many methods for working with text strings such as: Useful String methods method name type description charAt(...) char returns the character at a specified position (provided as the argument) where position is one of 0, 1, . . . , up to the length of the string. equals(. . . ) boolean used to determine if two strings are identical equalsIgnoreCase(. . . ) boolean used to determine if two strings are identical irrespective of case indexOf(. . . ) int returns the first position of a character provided as an argument, or -1 if it is not present length() int returns the length of a string toLowerCase() String converts all characters to lower case toUpperCase() String converts all characters to upper case trim() String removes leading spaces (blanks) and trailing spaces from a string Table 2.1: Some of the useful String methods At some time you should view the official documentation for the String class. Perhaps you will do this when you are developing a program and you want to look up the String methods. If you are using BlueJ its very easy to see the
Page 1 and 2: Java with BlueJ Part I Ron McFadyen
Page 3 and 4: To Callum 3
Page 5 and 6: Contents 1 Introduction 9 1.1 Java,
Page 7 and 8: Preface This book is Part I of a tw
Page 9 and 10: Chapter 1 Introduction This book is
Page 11 and 12: 1.2. THE JAVA COMPILER AND THE JAVA
Page 13 and 14: 1.4. A FIRST PROGRAM 13 1.4 A First
Page 15 and 16: 1.5. USING BLUEJ TO RUN HELLOWORLD
Page 17 and 18: 1.5. USING BLUEJ TO RUN HELLOWORLD
Page 19 and 20: Chapter 2 Basics This chapter cover
Page 21 and 22: 2.2. VARIABLES 21 Listing 2.1: Usin
Page 23 and 24: 2.3. PRIMITIVE DATA TYPES 23 Exerci
Page 25 and 26: 2.3. PRIMITIVE DATA TYPES 25 Defaul
Page 27 and 28: 2.3. PRIMITIVE DATA TYPES 27 14 Sys
Page 29 and 30: 2.3. PRIMITIVE DATA TYPES 29 2.3.3
Page 31 and 32: 2.3. PRIMITIVE DATA TYPES 31 Exampl
Page 33 and 34: 2.3. PRIMITIVE DATA TYPES 33 10 int
Page 35 and 36: 2.3. PRIMITIVE DATA TYPES 35 where
Page 37 and 38: 2.3. PRIMITIVE DATA TYPES 37 to kno
Page 39 and 40: 2.3. PRIMITIVE DATA TYPES 39 9 // D
Page 41 and 42: 2.3. PRIMITIVE DATA TYPES 41 use in
Page 43 and 44: 2.4. OPERATORS 43 2.4 Operators We
Page 45: 2.4. OPERATORS 45 odd statement to
Page 49 and 50: 2.5. THE STRING CLASS 49 name of th
Page 51 and 52: 2.5. THE STRING CLASS 51 Example, d
Page 53 and 54: 2.5. THE STRING CLASS 53 Exercises
Page 55 and 56: 2.6. OUTPUT 55 12 // Each time prin
Page 57 and 58: 2.6. OUTPUT 57 Test your program wi
Page 59 and 60: 2.6. OUTPUT 59 • Lines 14 and 15
Page 61 and 62: 2.7. INPUT 61 2.7 Input We examine
Page 63 and 64: 2.7. INPUT 63 Figure 2.8: Terminal
Page 65 and 66: 2.7. INPUT 65 2.7.2 The JOptionPane
Page 67 and 68: Chapter 3 Control Structures Progra
Page 69 and 70: 3.2. WHILE 69 A logical expression
Page 71 and 72: 3.2. WHILE 71 Figure 3.1: Output fr
Page 73 and 74: 3.2. WHILE 73 An example of output
Page 75 and 76: 3.2. WHILE 75 25 } 26 } Figure 3.2:
Page 77 and 78: 3.2. WHILE 77 Autoincrement Because
Page 79 and 80: 3.3. IF 79 Example 1 Suppose one ne
Page 81 and 82: 3.3. IF 81 Exercises 15. Write a pr
Page 83 and 84: 3.3. IF 83 9 { 10 public static voi
Page 85 and 86: 3.3. IF 85 Listing 3.6: Using an if
Page 87 and 88: 3.3. IF 87 the indentation. Each of
Page 89 and 90: 3.4. FOR 89 3.4 for The for stateme
Page 91 and 92: 3.4. FOR 91 Example 1 Below we use
Page 93 and 94: 3.4. FOR 93 Table 3.1: Process indi
Page 95 and 96: 3.4. FOR 95 Example 4 The program i
Page 97 and 98:
3.4. FOR 97 Example 5 In this examp
Page 99 and 100:
3.4. FOR 99 . . . Step 2, formattin
Page 101 and 102:
3.4. FOR 101 Exercises 20. Modify t
Page 103 and 104:
3.4. FOR 103 34. Modify the previou
Page 105 and 106:
3.5. DO ...WHILE 105 Example 1 Let
Page 107 and 108:
3.5. DO ...WHILE 107 Listing 3.16:
Page 109 and 110:
3.6. SWITCH 109 3.6 switch The swit
Page 111 and 112:
3.6. SWITCH 111 Example 1 Previousl
Page 113 and 114:
3.6. SWITCH 113 Exercises 39. Write
Page 115 and 116:
Chapter 4 Classes in the Java Class
Page 117 and 118:
4.1. RANDOM 117 Example 2 Consider
Page 119 and 120:
4.1. RANDOM 119 Exercises 1. Modify
Page 121 and 122:
4.2. CHARACTER 121 Example 1 Ifthed
Page 123 and 124:
4.2. CHARACTER 123 Example 2 The Ch
Page 125 and 126:
4.2. CHARACTER 125 Below is the out
Page 127 and 128:
4.3. SCANNER 127 4.3 Scanner Previo
Page 129 and 130:
4.3. SCANNER 129 Note that the abov
Page 131 and 132:
4.3. SCANNER 131
Page 133 and 134:
4.3. SCANNER 133 Exercises 11. Modi
Page 135 and 136:
4.4. MATH 135 The Math Class Fields
Page 137 and 138:
4.5. INTEGER 137 4.5 Integer The In
Page 139 and 140:
4.5. INTEGER 139 Listing 4.9: Using
Page 141 and 142:
Chapter 5 ArrayLists There are seve
Page 143 and 144:
143 The enhanced for Thereisavariat
Page 145 and 146:
145 Example 2 The contains() method
Page 147 and 148:
147 20 people.add(new Random()); 21
Page 149 and 150:
Chapter 6 One-Dimensional Arrays Th
Page 151 and 152:
6.1. INITIALIZING ARRAYS 151 6.1 In
Page 153 and 154:
6.3. THE ENHANCED FOR 153 6.3 The e
Page 155 and 156:
6.4. PASSING STRING VALUES INTO MAI
Page 157 and 158:
6.5. PARALLEL ARRAYS 157 18 } This
Page 159 and 160:
6.6. PARTIALLY FILLED ARRAYS 159 Th
Page 161 and 162:
6.7. ARRAY UTILITIES IN JAVA CLASS
Page 163 and 164:
6.7. ARRAY UTILITIES IN JAVA CLASS
Page 165 and 166:
Chapter 7 Designing Java Classes Up
Page 167 and 168:
7.1. USING MULTIPLE CLASSES 167 7.1
Page 169 and 170:
7.2. FIELDS 169 Figure 7.2: Class d
Page 171 and 172:
7.3. METHODS 171 7.3 Methods A meth
Page 173 and 174:
7.3. METHODS 173 Calling the other
Page 175 and 176:
7.3. METHODS 175 void methods Somet
Page 177 and 178:
7.4. CONSTRUCTORS 177 10 private St
Page 179 and 180:
7.4. CONSTRUCTORS 179 Using constru
Page 181 and 182:
7.5. VISIBILITY SPECIFICATIONS: PUB
Page 183 and 184:
7.7. ASSOCIATIONS 183 7.7 Associati
Page 185 and 186:
7.7. ASSOCIATIONS 185 Notice that t
Page 187 and 188:
7.7. ASSOCIATIONS 187 Now reconside
Page 189 and 190:
7.8. REUSING CODE 189 24 } The outp
Page 191 and 192:
7.9. PARAMETER LISTS AND ARGUMENTS
Page 193 and 194:
7.10. VARARGS: A VARIABLE NUMBER OF
Page 195 and 196:
7.11. CODE LISTINGS: STUDENT, SUBJE
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Chapter 8 A Brief Introduction to G
Page 205 and 206:
8.1. BRIEF INTRODUCTION TO SIMPLE G
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223:
Bibliography [1] http://publication
show all

Java with BlueJ, 2016a

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?