1. Chapter 20 – Java Utilities Package and Bit Manipulation
Outline
Introduction Vector Class and Enumeration Interface Stack Class Dictionary Class Hashtable Class Properties Class Random Class Bit Manipulation and the Bitwise Operators BitSet Class

2. Utility classes and interfaces
Introduction
Utility classes and interfaces
Contained in package java.util
Class Vector
Interface Enumeration
Class Stack
Class Dictionary
Class Hashtable
Class Properties
Class Random
Class BitSet

3. 20.2 Vector Class and Enumeration Interface
Class java.util.Vector
Array-like data structure that can resize itself dynamically
Contains a capacity
Grows by capacity increment if it requires additional space

4. Fig. 20.1 Demonstrating class Vector of package java.util. Line 26
1 // Fig. 20.1: VectorTest.java
2 // Testing the Vector class of the java.util package 3
4 // Java core packages
5 import java.util.*;
6 import java.awt.*;
7 import java.awt.event.*; 8
9 // Java extension packages
10 import javax.swing.*; 11
12 public class VectorTest extends JFrame {
private JLabel statusLabel;
private Vector vector;
private JTextField inputField; 16
// set up GUI to test Vector methods
public VectorTest() {
super( "Vector Example" ); 21
Container container = getContentPane();
container.setLayout( new FlowLayout() ); 24
statusLabel = new JLabel();
vector = new Vector( 1 ); 27
container.add( new JLabel( "Enter a string" ) ); 29
inputField = new JTextField( 10 );
container.add( inputField ); 32
// button to add element to vector
JButton addButton = new JButton( "Add" ); 35
Fig Demonstrating class Vector of package java.util. Line 26
Create Vector with initial capacity of one element

5. Vector method addElement appends Object to Vector
addButton.addActionListener( 37
new ActionListener() { 39
public void actionPerformed( ActionEvent event ) {
// add an element to vector
vector.addElement( inputField.getText() );
statusLabel.setText( "Added to end: " +
inputField.getText() );
inputField.setText( "" ); } }
); // end call to addActionListener 50
container.add( addButton ); 52
// button to remove element from vector
JButton removeButton = new JButton( "Remove" ); 55
removeButton.addActionListener( 57
new ActionListener() { 59
public void actionPerformed( ActionEvent event ) {
// remove element from vector
if ( vector.removeElement( inputField.getText() ) )
statusLabel.setText( "Removed: " +
inputField.getText() );
else
statusLabel.setText( inputField.getText() +
" not in vector" ); } }
Fig Demonstrating class Vector of package java.util (Part 2). Line 43 Lines 63-65
Vector method addElement appends Object to Vector
Vector method removeElement removes Object from Vector

6. Vector method firstElement obtains first Object in Vector
); // end call to addActionListener 72
container.add( removeButton ); 74
// button to get first element of vector
JButton firstButton = new JButton( "First" ); 77
firstButton.addActionListener( 79
new ActionListener() { 81
public void actionPerformed( ActionEvent event ) {
// return first element of vector
try {
statusLabel.setText(
"First element: " + vector.firstElement() ); } 89
// catch exception if Vector empty
catch ( NoSuchElementException exception ) {
statusLabel.setText( exception.toString() ); } } }
); // end call to addActionListener 97
container.add( firstButton ); 99
// button to get last element of vector
JButton lastButton = new JButton( "Last" );
102
lastButton.addActionListener(
104
Fig Demonstrating class Vector of package java.util (Part 3). Line 87
Vector method firstElement obtains first Object in Vector

7. Vector method lastElement obtains last Object in Vector
new ActionListener() {
106
public void actionPerformed( ActionEvent event ) {
// return last element of vector
try {
statusLabel.setText(
"Last element: " + vector.lastElement() ); }
114
// catch exception if Vector empty
catch ( NoSuchElementException exception ) {
statusLabel.setText( exception.toString() ); } } }
); // end call to addActionListener
122
container.add( lastButton );
124
// button to determine whether vector is empty
JButton emptyButton = new JButton( "Is Empty?" );
127
emptyButton.addActionListener(
129
new ActionListener() {
131
public void actionPerformed( ActionEvent event ) {
// determine if Vector is empty
statusLabel.setText( vector.isEmpty() ?
"Vector is empty" : "Vector is not empty" ); } }
); // end call to addActionListener
Vector method lastElement obtains last Object in Vector
Fig Demonstrating class Vector of package java.util (Part 4). Line 112 Line 135
Vector method isEmpty returns boolean that indicates whether Vector contains any Objects

8. 140
container.add( emptyButton );
142
// button to determine whether vector contains search key
JButton containsButton = new JButton( "Contains" );
145
containsButton.addActionListener(
147
new ActionListener() {
149
public void actionPerformed( ActionEvent event ) {
String searchKey = inputField.getText();
153
// determine if Vector contains searchKey
if ( vector.contains( searchKey ) )
statusLabel.setText(
"Vector contains " + searchKey );
else
statusLabel.setText(
"Vector does not contain " + searchKey ); } }
); // end call to addActionListener
164
container.add( containsButton );
166
// button to determine location of value in vector
JButton locationButton = new JButton( "Location" );
169
locationButton.addActionListener(
171
new ActionListener() {
173
Fig Demonstrating class Vector of package java.util (Part 5). Line 155
Vector method contains returns boolean that indicates whether Vector contains a specific Object

9. 174 public void actionPerformed( ActionEvent event ){
// get location of an object in Vector
statusLabel.setText( "Element is at location " +
vector.indexOf( inputField.getText() ) ); } }
); // end call to addActionListener
182
container.add( locationButton );
184
// button to trim vector size
JButton trimButton = new JButton( "Trim" );
187
trimButton.addActionListener(
189
new ActionListener() {
191
public void actionPerformed( ActionEvent event ) {
// remove unoccupied elements to save memory
vector.trimToSize();
statusLabel.setText( "Vector trimmed to size" ); } } );
200
container.add( trimButton );
202
// button to display vector size and capacity
JButton statsButton = new JButton( "Statistics" );
205
statsButton.addActionListener(
207
Fig Demonstrating class Vector of package java.util (Part 6). Line 178 Line 195
Vector method indexOf returns index of first location in Vector containing the argument
Vector method trimToSize reduces the Vector capacity to the current number of elements in Vector

10. 208 new ActionListener() {
209
public void actionPerformed( ActionEvent event ) {
// get size and capacity of Vector
statusLabel.setText( "Size = " + vector.size() +
"; capacity = " + vector.capacity() ); } }
); // end call to addActionListener
218
container.add( statsButton );
220
// button to display vector contents
JButton displayButton = new JButton( "Display" );
223
displayButton.addActionListener(
225
new ActionListener() {
227
public void actionPerformed( ActionEvent event ) {
// use Enumeration to output Vector contents
Enumeration enum = vector.elements();
StringBuffer buf = new StringBuffer();
233
while ( enum.hasMoreElements() )
buf.append( enum.nextElement() ).append( " " );
236
JOptionPane.showMessageDialog( null,
buf.toString(), "Display",
JOptionPane.PLAIN_MESSAGE ); } }
); // end call to addActionListener
Fig Demonstrating class Vector of package java.util (Part 7). Lines Line 231
Vector methods size and capacity return number of Objects in Vector and Vector capacity, respectively
Vector method elements returns Enumeration for iterating Vector elements

11. 243
container.add( displayButton );
container.add( statusLabel );
246
setSize( 300, 200 );
setVisible( true );
249
} // end VectorTest constructor
251
// execute application
public static void main( String args[] ) {
VectorTest application = new VectorTest();
256
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); }
260
261 } // end class VectorTest
Fig Demonstrating class Vector of package java.util (Part 8) Program Output

12. 20.3 Stack Class Stack Implements stack data structure
Extends class Vector
Stores references to Objects (as does Vector)

13. Fig. 20.2 Demonstrating class Stack of package java.util. Line 25
1 // Fig. 20.2: StackTest.java
2 // Testing the Stack class of the java.util package 3
4 // Java core packages
5 import java.awt.*;
6 import java.awt.event.*;
7 import java.util.*; 8
9 // Java extension packages
10 import javax.swing.*; 11
12 public class StackTest extends JFrame {
private JLabel statusLabel;
private JTextField inputField;
private Stack stack; 16
// create GUI to manipulate a Stack
public StackTest() {
super( "Stacks" ); 21
Container container = getContentPane(); 23
statusLabel = new JLabel();
stack = new Stack(); 26
container.setLayout( new FlowLayout() );
container.add( new JLabel( "Enter a string" ) );
inputField = new JTextField( 10 );
container.add( inputField ); 31
// button to place object on stack
JButton pushButton = new JButton( "Push" ); 34
Fig Demonstrating class Stack of package java.util. Line 25
Create empty Stack

14. Stack method push adds Object argument to top of Stack
pushButton.addActionListener( 36
new ActionListener() { 38
public void actionPerformed( ActionEvent event ) {
// put object on Stack
statusLabel.setText( "Pushed: " +
stack.push( inputField.getText() ) ); } } ); 47
container.add( pushButton ); 49
// button to remove top object on stack
JButton popButton = new JButton( "Pop" ); 52
popButton.addActionListener( 54
new ActionListener() { 56
public void actionPerformed( ActionEvent event ) {
// remove element from Stack
try {
statusLabel.setText( "Popped: " + stack.pop() ); } 63
// process exception if Stack empty
catch ( EmptyStackException exception ) {
statusLabel.setText( exception.toString() ); } } }
Fig Demonstrating class Stack of package java.util (Part 2). Line 43 Line 61
Stack method push adds Object argument to top of Stack
Stack method pop removes Object from top of Stack

15. ); 71
container.add( popButton ); 73
// button to look at top element of stack
JButton peekButton = new JButton( "Peek" ); 76
peekButton.addActionListener( 78
new ActionListener() { 80
public void actionPerformed( ActionEvent event ) {
// look at top object on Stack
try {
statusLabel.setText( "Top: " + stack.peek() ); } 87
// process exception if Stack empty
catch ( EmptyStackException exception ) {
statusLabel.setText( exception.toString() ); } } } ); 95
container.add( peekButton ); 97
// button to determine whether stack is empty
JButton emptyButton = new JButton( "Is Empty?" );
100
emptyButton.addActionListener(
102
new ActionListener() {
104
Fig Demonstrating class Stack of package java.util (Part 3). Line 85
Stack method peek returns Object from top of Stack, without removing that Object

16. 105 public void actionPerformed( ActionEvent event ){
// determine if Stack is empty
statusLabel.setText( stack.empty() ?
"Stack is empty" : "Stack is not empty" ); } } );
113
container.add( emptyButton );
115
// button to determine whether search key is in stack
JButton searchButton = new JButton( "Search" );
118
searchButton.addActionListener(
120
new ActionListener() {
122
public void actionPerformed( ActionEvent event ) {
// search Stack for specified object
String searchKey = inputField.getText();
int result = stack.search( searchKey );
128
if ( result == -1 )
statusLabel.setText( searchKey + " not found" );
else
statusLabel.setText( searchKey +
" found at element " + result ); } } );
137
container.add( searchButton );
139
Fig Demonstrating class Stack of package java.util (Part 4). Line 108 Line 127
Stack method empty returns boolean that indicates whether Stack contains any Objects
Stack method search returns boolean that indicates whether Stack contains specific Object argument

17. 140 // button to display stack contents
JButton displayButton = new JButton( "Display" );
142
displayButton.addActionListener(
144
new ActionListener() {
146
public void actionPerformed( ActionEvent event ) {
// output Stack contents
Enumeration enumeration = stack.elements();
StringBuffer buffer = new StringBuffer();
152
while ( enumeration.hasMoreElements() )
buffer.append(
enumeration.nextElement() ).append( " " );
156
JOptionPane.showMessageDialog( null,
buffer.toString(), "Display",
JOptionPane.PLAIN_MESSAGE ); } } );
163
container.add( displayButton );
container.add( statusLabel );
166
setSize( 675, 100 );
setVisible( true ); }
170
Fig Demonstrating class Stack of package java.util (Part 5). Line 150
Stack extends Vector, so class Stack may use method elements to obtain Enumeration for Stack

18. 171 // execute application
public static void main( String args[] ) {
StackTest application = new StackTest();
175
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); }
179
180 } // end class StackTest
Fig Demonstrating class Stack of package java.util (Part 6). Program Output

19. 20.4 Dictionary Class Dictionary Maps keys to values
Provides public interface
Methods required to maintain table of key-value pairs
abstract class
Superclass of class Hashtable

20. 20.5 Hashtable Class Hashtable Data structure that use hashing
Algorithm for determining a key in table
Keys in tables have associated values (data)
Each table cell is a hash “bucket”
Linked list of all key-value pairs that hash to that cell
Minimizes collisions

21. Fig. 20.3 Demonstrating class Hashtable. Line 25
1 // Fig. 20.3: HashtableTest.java
2 // Demonstrates class Hashtable of the java.util package. 3
4 // Java core packages
5 import java.awt.*;
6 import java.awt.event.*;
7 import java.util.*; 8
9 // Java extensions packages
10 import javax.swing.*; 11
12 public class HashtableTest extends JFrame {
private JLabel statusLabel;
private Hashtable table;
private JTextArea displayArea;
private JTextField lastNameField;
private JTextField firstNameField; 18
// set up GUI to demonstrate Hashtable features
public HashtableTest() {
super( "Hashtable Example" ); 23
statusLabel = new JLabel();
table = new Hashtable();
displayArea = new JTextArea( 4, 20 );
displayArea.setEditable( false ); 28
JPanel northSubPanel = new JPanel(); 30
northSubPanel.add( new JLabel( "First name" ) );
firstNameField = new JTextField( 8 );
northSubPanel.add( firstNameField ); 34
Fig Demonstrating class Hashtable. Line 25
Create empty Hashtable

22. Fig. 20.3 Demonstrating class Hashtable (Part 2). Lines 59-60
northSubPanel.add( new JLabel( "Last name (key)" ) );
lastNameField = new JTextField( 8 );
northSubPanel.add( lastNameField ); 38
JPanel northPanel = new JPanel();
northPanel.setLayout( new BorderLayout() );
northPanel.add( northSubPanel, BorderLayout.NORTH );
northPanel.add( statusLabel, BorderLayout.SOUTH ); 43
JPanel southPanel = new JPanel();
southPanel.setLayout( new GridLayout( 2, 5 ) );
JButton putButton = new JButton( "Put" ); 47
putButton.addActionListener( 49
new ActionListener() { 51
// add new key/value pair to hash table
public void actionPerformed( ActionEvent event ) {
Employee employee = new Employee(
firstNameField.getText(),
lastNameField.getText() ); 58
Object value =
table.put( lastNameField.getText(), employee ); 61
// first time this key was added
if ( value == null )
statusLabel.setText(
"Put: " + employee.toString() ); 66
Fig Demonstrating class Hashtable (Part 2). Lines 59-60
Hashtable method put adds key and value to Hashtable (returns null if key has been inserted previously)

23. Fig. 20.3 Demonstrating class Hashtable (Part 3). Line 88
// replaced previous value for this key
else
statusLabel.setText(
"Put: " + employee.toString() +
"; Replaced: " + value.toString() ); } } ); 75
southPanel.add( putButton ); 77
// button to get value for specific key
JButton getButton = new JButton( "Get" ); 80
getButton.addActionListener( 82
new ActionListener() { 84
// get value for specific key
public void actionPerformed( ActionEvent event ) {
Object value = table.get( lastNameField.getText() ); 89
// value found for key
if ( value != null )
statusLabel.setText(
"Get: " + value.toString() ); 94
// value not found for key
else
statusLabel.setText(
"Get: " + lastNameField.getText() +
" not in table" ); } }
Fig Demonstrating class Hashtable (Part 3). Line 88
Hashtable method get obtains Object associated with key from Hashtable (returns null if neither key nor Object exist)

24. Fig. 20.3 Demonstrating class Hashtable (Part 4). Lines 116-117);
103
southPanel.add( getButton );
105
// button to remove key/value pair from table
JButton removeButton = new JButton( "Remove" );
108
removeButton.addActionListener(
110
new ActionListener() {
112
// remove key/value pair
public void actionPerformed( ActionEvent event ) {
Object value =
table.remove( lastNameField.getText() );
118
// key found
if ( value != null )
statusLabel.setText( "Remove: " +
value.toString() );
123
// key not found
else
statusLabel.setText( "Remove: " +
lastNameField.getText() + " not in table" ); } } );
131
southPanel.add( removeButton );
133
// button to detetmine whether hash table is empty
JButton emptyButton = new JButton( "Empty" );
136
Fig Demonstrating class Hashtable (Part 4). Lines
Hashtable method remove removes Object associated with key argument from Hashtable

25. Hashtable method isEmpty returns boolean that indicates whether Hashtable contains any Objects
emptyButton.addActionListener(
138
new ActionListener() {
140
// determine whether hash table is empty
public void actionPerformed( ActionEvent event ) {
statusLabel.setText( "Empty: " + table.isEmpty() ); } } );
148
southPanel.add( emptyButton );
150
// button to determine whether hash table contains key
JButton containsKeyButton = new JButton( "Contains key" );
153
containsKeyButton.addActionListener(
155
new ActionListener() {
157
// determine whether hash table contains key
public void actionPerformed( ActionEvent event ) {
statusLabel.setText( "Contains key: " +
table.containsKey( lastNameField.getText() ) ); } } );
166
southPanel.add( containsKeyButton );
168
// button to clear all hash table contents
JButton clearButton = new JButton( "Clear table" );
171
Fig Demonstrating class Hashtable (Part 5). Line 144 Lines
Hashtable method containsKey returns boolean that indicates whether Hashtable contains key argument

26. Hashtable method clear removes all elements from Hashtable
clearButton.addActionListener(
173
new ActionListener() {
175
// clear hash table contents
public void actionPerformed( ActionEvent event ) {
table.clear();
statusLabel.setText( "Clear: Table is now empty" ); } } );
184
southPanel.add( clearButton );
186
// button to display hash table elements
JButton listElementsButton = new JButton( "List objects" );
189
listElementsButton.addActionListener(
191
new ActionListener() {
193
// display hash table elements
public void actionPerformed( ActionEvent event ) {
StringBuffer buffer = new StringBuffer();
198
for ( Enumeration enumeration = table.elements();
enumeration.hasMoreElements(); )
buffer.append(
enumeration.nextElement() ).append( '\n' );
203
displayArea.setText( buffer.toString() ); } }
Fig Demonstrating class Hashtable (Part 6). Line 179 Lines
Hashtable method clear removes all elements from Hashtable
Hashtable method elements obtains Enumeration of Hashtable values

27. Fig. 20.3 Demonstrating class Hashtable (Part 7). Lines 223-224);
208
southPanel.add( listElementsButton );
210
// button to display hash table keys
JButton listKeysButton = new JButton( "List keys" );
213
listKeysButton.addActionListener(
215
new ActionListener() {
217
// display hash table KEYS
public void actionPerformed( ActionEvent event ) {
StringBuffer buffer = new StringBuffer();
222
for ( Enumeration enumeration = table.keys();
enumeration.hasMoreElements(); )
buffer.append(
enumeration.nextElement() ).append( '\n' );
227
JOptionPane.showMessageDialog( null,
buffer.toString(), "Display",
JOptionPane.PLAIN_MESSAGE ); } } );
234
southPanel.add( listKeysButton );
236
Container container = getContentPane();
container.add( northPanel, BorderLayout.NORTH );
container.add( new JScrollPane( displayArea ),
BorderLayout.CENTER );
container.add( southPanel, BorderLayout.SOUTH );
Fig Demonstrating class Hashtable (Part 7). Lines
Hashtable method keys obtains Enumeration of Hashtable keys

28. Fig. 20.3 Demonstrating class Hashtable (Part 8).
242
setSize( 540, 300 );
setVisible( true ); }
246
// execute application
public static void main( String args[] ) {
HashtableTest application = new HashtableTest();
251
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); }
255
256 } // end class HashtableTest
257
258 // Employee class to represent first and last name
259 class Employee {
private String first, last;
261
// initialize an Employee
public Employee( String firstName, String lastName ) {
first = firstName;
last = lastName; }
268
// convert Employee to String representation
public String toString() {
return first + " " + last; }
274
275 } // end class Employee
Fig Demonstrating class Hashtable (Part 8).

29. Fig. 20.3 Demonstrating class Hashtable (Part 9). Program Output

30. 20.6 Properties Class Properties Persistent Hashtable
Can be written to output stream and directed to file
Can be read from file into input stream
Provides methods setProperty and getProperty
Store/obtain key-value pairs of Strings

31. Fig. 20.4 Demonstrating class Properties. Line 25
1 // Fig. 20.4: PropertiesTest.java
2 // Demonstrates class Properties of the java.util package. 3
4 // Java core packages
5 import java.awt.*;
6 import java.awt.event.*;
7 import java.io.*;
8 import java.util.*; 9
10 // Java extension packages
11 import javax.swing.*; 12
13 public class PropertiesTest extends JFrame {
private JLabel statusLabel;
private Properties table;
private JTextArea displayArea;
private JTextField valueField, nameField; 18
// set up GUI to test Properties table
public PropertiesTest() {
super( "Properties Test" ); 23
// create Properties table
table = new Properties(); 26
Container container = getContentPane(); 28
// set up NORTH of window's BorderLayout
JPanel northSubPanel = new JPanel(); 31
northSubPanel.add( new JLabel( "Property value" ) );
valueField = new JTextField( 10 );
northSubPanel.add( valueField ); 35
Fig Demonstrating class Properties. Line 25
Create empty Properties

32. Fig. 20.4 Demonstrating class Properties (Part 2). Lines 68-69
northSubPanel.add( new JLabel( "Property name (key)" ) );
nameField = new JTextField( 10 );
northSubPanel.add( nameField ); 39
JPanel northPanel = new JPanel();
northPanel.setLayout( new BorderLayout() );
northPanel.add( northSubPanel, BorderLayout.NORTH ); 43
statusLabel = new JLabel();
northPanel.add( statusLabel, BorderLayout.SOUTH ); 46
container.add( northPanel, BorderLayout.NORTH ); 48
// set up CENTER of window's BorderLayout
displayArea = new JTextArea( 4, 35 );
container.add( new JScrollPane( displayArea ),
BorderLayout.CENTER ); 53
// set up SOUTH of window's BorderLayout
JPanel southPanel = new JPanel();
southPanel.setLayout( new GridLayout( 1, 5 ) ); 57
// button to put a name/value pair in Properties table
JButton putButton = new JButton( "Put" ); 60
putButton.addActionListener( 62
new ActionListener() { 64
// put name/value pair in Properties table
public void actionPerformed( ActionEvent event ) {
Object value = table.setProperty(
nameField.getText(), valueField.getText() ); 70
Fig Demonstrating class Properties (Part 2). Lines 68-69
Properties method setProperty stores value for the specified key

33. Fig. 20.4 Demonstrating class Properties (Part 3).
if ( value == null )
showstatus( "Put: " + nameField.getText() +
" " + valueField.getText() ); 74
else
showstatus( "Put: " + nameField.getText() +
" " + valueField.getText() +
"; Replaced: " + value.toString() ); 79
listProperties(); } }
); // end call to addActionListener 84
southPanel.add( putButton ); 86
// button to empty contents of Properties table
JButton clearButton = new JButton( "Clear" ); 89
clearButton.addActionListener( 91
new ActionListener() { 93
// use method clear to empty table
public void actionPerformed( ActionEvent event ) {
table.clear();
showstatus( "Table in memory cleared" );
listProperties(); } }
); // end call to addActionListener
103
southPanel.add( clearButton );
105
Fig Demonstrating class Properties (Part 3).

34. Fig. 20.4 Demonstrating class Properties (Part 4). Lines 116-117
// button to get value of a property
JButton getPropertyButton = new JButton( "Get property" );
108
getPropertyButton.addActionListener(
110
new ActionListener() {
112
// use method getProperty to obtain a property value
public void actionPerformed( ActionEvent event ) {
Object value = table.getProperty(
nameField.getText() );
118
if ( value != null )
showstatus( "Get property: " +
nameField.getText() + " " +
value.toString() );
123
else
showstatus( "Get: " + nameField.getText() +
" not in table" );
127
listProperties(); } }
); // end call to addActionListener
132
southPanel.add( getPropertyButton );
134
// button to contents of Properties table to file
JButton saveButton = new JButton( "Save" );
137
saveButton.addActionListener(
139
Fig Demonstrating class Properties (Part 4). Lines
Properties method getProperty locates value associated with the specified key

35. Fig. 20.4 Demonstrating class Properties (Part 5). Line 150
new ActionListener() {
141
// use method save to place contents in file
public void actionPerformed( ActionEvent event ) {
// save contents of table
try {
FileOutputStream output =
new FileOutputStream( "props.dat" );
149
table.store( output, "Sample Properties" );
output.close();
152
listProperties(); }
155
// process problems with file output
catch( IOException ioException ) {
ioException.printStackTrace(); } } }
); // end call to addActionListener
163
southPanel.add( saveButton );
165
// button to load contents of Properties table from file
JButton loadButton = new JButton( "Load" );
168
loadButton.addActionListener(
170
new ActionListener() {
172
Fig Demonstrating class Properties (Part 5). Line 150
Properties method store saves Properties contents to FileOutputStream

36. Fig. 20.4 Demonstrating class Properties (Part 6). Line 181
// use method load to read contents from file
public void actionPerformed( ActionEvent event ) {
// load contents of table
try {
FileInputStream input =
new FileInputStream( "props.dat" );
180
table.load( input );
input.close();
listProperties(); }
185
// process problems with file input
catch( IOException ioException ) {
ioException.printStackTrace(); } } }
); // end call to addActionListener
193
southPanel.add( loadButton );
195
container.add( southPanel, BorderLayout.SOUTH );
197
setSize( 550, 225 );
setVisible( true ); }
201
// output property values
public void listProperties() {
StringBuffer buffer = new StringBuffer();
String name, value;
207
Fig Demonstrating class Properties (Part 6). Line 181
Properties method load restores Properties contents from FileInputStream

37. Fig. 20.4 Demonstrating class Properties (Part 7). Line 208
Enumeration enumeration = table.propertyNames();
209
while ( enumeration.hasMoreElements() ) {
name = enumeration.nextElement().toString();
value = table.getProperty( name );
213
buffer.append( name ).append( '\t' );
buffer.append( value ).append( '\n' ); }
217
displayArea.setText( buffer.toString() );
} // end method ListProperties
220
// display String in statusLabel label
public void showstatus( String s ) {
statusLabel.setText( s ); }
226
// execute application
public static void main( String args[] ) {
PropertiesTest application = new PropertiesTest();
231
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); }
235
236 } // end class PropertiesTest
Properties method propertyNames obtains Enumeration of property names
Fig Demonstrating class Properties (Part 7). Line 208

38. Fig. 20.4 Demonstrating class Properties (Part 8). Program Output

39. 20.7 Random Class Class Random
Provides (pseudo-) random-number generation
Random r = new Random();
Use seed to generate same random-number sequences
Random r = new Random( seedValue );
(useful when debugging)
Can generate distributed numbers uniformly
r.nextInt();
r.nextFloat();
Use % operator to scale generated number
e.g., rolling a six-sided die
Math.abs( r.nextInt() ) % 6 + 1;

40. 20.8 Bit Manipulation and the Bitwise Operators
Used for bit manipulation
Used for getting down to “bit-and-bytes” level

41. 20.8 Bit Manipulation and the Bitwise Operators (cont.)

42. Fig. 20.6 Printing the bits in an integer.
1 // Fig. 20.6: PrintBits.java
2 // Printing an unsigned integer in bits 3
4 // Java core packages
5 import java.awt.*;
6 import java.awt.event.*; 7
8 // Java extension packages
9 import javax.swing.*; 10
11 public class PrintBits extends JFrame {
private JTextField outputField; 13
// set up GUI
public PrintBits() {
super( "Printing bit representations for numbers" ); 18
Container container = getContentPane();
container.setLayout( new FlowLayout() ); 21
container.add( new JLabel( "Enter an integer " ) ); 23
// textfield to read value from user
JTextField inputField = new JTextField( 10 ); 26
inputField.addActionListener( 28
new ActionListener() { 30
Fig Printing the bits in an integer.

43. 31 // read integer and get bitwise representation
public void actionPerformed( ActionEvent event ) {
int value = Integer.parseInt(
event.getActionCommand() );
outputField.setText( getBits( value ) ); } } ); 40
container.add( inputField ); 42
container.add( new JLabel( "The integer in bits is" ) ); 44
// textfield to display integer in bitwise form
outputField = new JTextField( 33 );
outputField.setEditable( false );
container.add( outputField ); 49
setSize( 720, 70 );
setVisible( true ); } 53
// display bit representation of specified int value
private String getBits( int value ) {
// create int value with 1 in leftmost bit and 0s elsewhere
int displayMask = 1 << 31; 59
// buffer to build output
StringBuffer buffer = new StringBuffer( 35 ); 62
// for each bit append 0 or 1 to buffer
for ( int bit = 1; bit <= 32; bit++ ) { 65
Fig Printing the bits in an integer (Part 2). Lines Line 58
Convert String to int, then pass int to private method getBits to get the int’s bit representation
1 << 31 equals

44. Fig. 20.6 Printing the bits in an integer (Part 3). Line 69
// use displayMask to isolate bit and determine whether
// bit has value of 0 or 1
buffer.append(
( value & displayMask ) == 0 ? '0' : '1' ); 70
// shift value one position to left
value <<= 1; 73
// append space to buffer every 8 bits
if ( bit % 8 == 0 )
buffer.append( ' ' ); } 78
return buffer.toString(); } 81
// execute application
public static void main( String args[] ) {
PrintBits application = new PrintBits(); 86
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); } 90
91 } // end class PrintBits
Fig Printing the bits in an integer (Part 3). Line 69
Use bitwise AND (&) to combine each bit in value and 1 << 31

45. Fig. 20.6 Printing the bits in an integer (Part 4). Program Output

46. 20.8 Bit manipulation and the Bitwise Operators (cont.)

47. 1 // Fig. 20.8: MiscBitOps.java
2 // Using the bitwise AND, bitwise inclusive OR, bitwise
3 // exclusive OR, and bitwise complement operators. 4
5 // Java core packages
6 import java.awt.*;
7 import java.awt.event.*; 8
9 // Java extension packages
10 import javax.swing.*; 11
12 public class MiscBitOps extends JFrame {
private JTextField input1Field, input2Field,
bits1Field, bits2Field, bits3Field, resultField;
private int value1, value2; 16
// set up GUI
public MiscBitOps() {
super( "Bitwise operators" ); 21
JPanel inputPanel = new JPanel();
inputPanel.setLayout( new GridLayout( 4, 2 ) ); 24
inputPanel.add( new JLabel( "Enter 2 ints" ) );
inputPanel.add( new JLabel( "" ) ); 27
inputPanel.add( new JLabel( "Value 1" ) );
input1Field = new JTextField( 8 );
inputPanel.add( input1Field ); 31
inputPanel.add( new JLabel( "Value 2" ) );
input2Field = new JTextField( 8 );
inputPanel.add( input2Field ); 35
Fig Demonstrating the bitwise AND, bitwise inclusive OR, bitwise exclusive OR and bitwise complement operators.

48. 36 inputPanel.add( new JLabel( "Result" ) );
resultField = new JTextField( 8 );
resultField.setEditable( false );
inputPanel.add( resultField ); 40
JPanel bitsPanel = new JPanel();
bitsPanel.setLayout( new GridLayout( 4, 1 ) );
bitsPanel.add( new JLabel( "Bit representations" ) ); 44
bits1Field = new JTextField( 33 );
bits1Field.setEditable( false );
bitsPanel.add( bits1Field ); 48
bits2Field = new JTextField( 33 );
bits2Field.setEditable( false );
bitsPanel.add( bits2Field ); 52
bits3Field = new JTextField( 33 );
bits3Field.setEditable( false );
bitsPanel.add( bits3Field ); 56
JPanel buttonPanel = new JPanel(); 58
// button to perform bitwise AND
JButton andButton = new JButton( "AND" ); 61
andButton.addActionListener( 63
new ActionListener() { 65
Fig Demonstrating the bitwise AND, bitwise inclusive OR, bitwise exclusive OR and bitwise complement operators (Part 2).

49. Use bitwise AND (&) to combine value1 and value2
// perform bitwise AND and display results
public void actionPerformed( ActionEvent event ) {
setFields();
resultField.setText(
Integer.toString( value1 & value2 ) );
bits3Field.setText( getBits( value1 & value2 ) ); } } ); 76
buttonPanel.add( andButton ); 78
// button to perform bitwise inclusive OR
JButton inclusiveOrButton = new JButton( "Inclusive OR" ); 81
inclusiveOrButton.addActionListener( 83
new ActionListener() { 85
// perform bitwise inclusive OR and display results
public void actionPerformed( ActionEvent event ) {
setFields();
resultField.setText(
Integer.toString( value1 | value2 ) );
bits3Field.setText( getBits( value1 | value2 ) ); } } ); 96
buttonPanel.add( inclusiveOrButton ); 98
Use bitwise AND (&) to combine value1 and value2
Fig Demonstrating the bitwise AND, bitwise inclusive OR, bitwise exclusive OR and bitwise complement operators (Part 3). Line 71 Line 91
Use bitwise inclusive OR (|) to combine value1 and value2

50. Use bitwise exclusive OR (^) to combine value1 and value2
// button to perform bitwise exclusive OR
JButton exclusiveOrButton = new JButton( "Exclusive OR" );
101
exclusiveOrButton.addActionListener(
103
new ActionListener() {
105
// perform bitwise exclusive OR and display results
public void actionPerformed( ActionEvent event ) {
setFields();
resultField.setText(
Integer.toString( value1 ^ value2 ) );
bits3Field.setText( getBits( value1 ^ value2 ) ); } } );
116
buttonPanel.add( exclusiveOrButton );
118
// button to perform bitwise complement
JButton complementButton = new JButton( "Complement" );
121
complementButton.addActionListener(
123
new ActionListener() {
125
// perform bitwise complement and display results
public void actionPerformed( ActionEvent event ) {
input2Field.setText( "" );
bits2Field.setText( "" );
131
int value = Integer.parseInt( input1Field.getText() );
133
Fig Demonstrating the bitwise AND, bitwise inclusive OR, bitwise exclusive OR and bitwise complement operators (Part 4). Line 111
Use bitwise exclusive OR (^) to combine value1 and value2

51. Use bitwise complement (~) on value
resultField.setText( Integer.toString( ~value ) );
bits1Field.setText( getBits( value ) );
bits3Field.setText( getBits( ~value ) ); } } );
140
buttonPanel.add( complementButton );
142
Container container = getContentPane();
container.add( inputPanel, BorderLayout.WEST );
container.add( bitsPanel, BorderLayout.EAST );
container.add( buttonPanel, BorderLayout.SOUTH );
147
setSize( 600, 150 );
setVisible( true ); }
151
// display numbers and their bit form
private void setFields() {
value1 = Integer.parseInt( input1Field.getText() );
value2 = Integer.parseInt( input2Field.getText() );
157
bits1Field.setText( getBits( value1 ) );
bits2Field.setText( getBits( value2 ) ); }
161
// display bit representation of specified int value
private String getBits( int value ) {
// create int value with 1 in leftmost bit and 0s elsewhere
int displayMask = 1 << 31;
167
Use bitwise complement (~) on value
Fig Demonstrating the bitwise AND, bitwise inclusive OR, bitwise exclusive OR and bitwise complement operators (Part 5). Line 134

52. 168 // buffer to build output
StringBuffer buffer = new StringBuffer( 35 );
170
// for each bit append 0 or 1 to buffer
for ( int bit = 1; bit <= 32; bit++ ) {
173
// use displayMask to isolate bit and determine whether
// bit has value of 0 or 1
buffer.append(
( value & displayMask ) == 0 ? '0' : '1' );
178
// shift value one position to left
value <<= 1;
181
// append space to buffer every 8 bits
if ( bit % 8 == 0 )
buffer.append( ' ' ); }
186
return buffer.toString(); }
189
// execute application
public static void main( String args[] ) {
MiscBitOps application = new MiscBitOps();
194
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); }
198
199 } // end class MiscBitOps
Fig Demonstrating the bitwise AND, bitwise inclusive OR, bitwise exclusive OR and bitwise complement operators (Part 6).

53. Fig Demonstrating the bitwise AND, bitwise inclusive OR, bitwise exclusive OR and bitwise complement operators (Part 7). Program Output

54. 20.8 Bit Manipulation and the Bitwise Operators (cont.)

55. 20.8 Bit Manipulation and the Bitwise Operators (cont.)

56. Fig. 20.11 Demonstrating the bitwise shift operators.
1 // Fig : BitShift.java
2 // Using the bitwise shift operators. 3
4 // Java core packages
5 import java.awt.*;
6 import java.awt.event.*; 7
8 // Java extension packages
9 import javax.swing.*; 10
11 public class BitShift extends JFrame {
private JTextField bitsField;
private JTextField valueField; 14
// set up GUI
public BitShift() {
super( "Shifting bits" ); 19
Container container = getContentPane();
container.setLayout( new FlowLayout() ); 22
container.add( new JLabel( "Integer to shift " ) ); 24
// textfield for user to input integer
valueField = new JTextField( 12 );
container.add( valueField ); 28
valueField.addActionListener( 30
new ActionListener() { 32
Fig Demonstrating the bitwise shift operators.

57. Fig. 20.11 Demonstrating the bitwise shift operators (Part 2). Line 58
// read value and display its bitwise representation
public void actionPerformed( ActionEvent event ) {
int value = Integer.parseInt( valueField.getText() );
bitsField.setText( getBits( value ) ); } } ); 41
// textfield to display bitwise representation of an integer
bitsField = new JTextField( 33 );
bitsField.setEditable( false );
container.add( bitsField ); 46
// button to shift bits left by one position
JButton leftButton = new JButton( "<<" ); 49
leftButton.addActionListener( 51
new ActionListener() { 53
// left shift one position and display new value
public void actionPerformed( ActionEvent event ) {
int value = Integer.parseInt( valueField.getText() );
value <<= 1;
valueField.setText( Integer.toString( value ) );
bitsField.setText( getBits( value ) ); } } ); 64
container.add( leftButton ); 66
Fig Demonstrating the bitwise shift operators (Part 2). Line 58
Use bitwise left-shift operator (<<) to shift value’s bits to the left by one position

58. 67 // button to right shift value one position with sign extension
JButton rightSignButton = new JButton( ">>" ); 69
rightSignButton.addActionListener( 71
new ActionListener() { 73
// right shift one position and display new value
public void actionPerformed( ActionEvent event ) {
int value = Integer.parseInt( valueField.getText() );
value >>= 1;
valueField.setText( Integer.toString( value ) );
bitsField.setText( getBits( value ) ); } } ); 84
container.add( rightSignButton ); 86
// button to right shift value one position with zero extension
JButton rightZeroButton = new JButton( ">>>" ); 89
rightZeroButton.addActionListener( 91
new ActionListener() { 93
// right shift one position and display new value
public void actionPerformed( ActionEvent event ) {
int value = Integer.parseInt( valueField.getText() );
value >>>= 1;
valueField.setText( Integer.toString( value ) );
100
bitsField.setText( getBits( value ) );
Use bitwise right-shift with signed extension operator (>>) to shift value’s bits to the right by one position
Fig Demonstrating the bitwise shift operators (Part 3). Line 78 Line 98
Use bitwise right-shift with unsigned extension operator (>>>) to shift value’s bits to the right by one position

59. Fig. 20.11 Demonstrating the bitwise shift operators (Part 4).} } );
105
container.add( rightZeroButton );
107
setSize( 400, 120 );
setVisible( true ); }
111
// display bit representation of specified int value
private String getBits( int value ) {
// create int value with 1 in leftmost bit and 0s elsewhere
int displayMask = 1 << 31;
117
// buffer to build output
StringBuffer buffer = new StringBuffer( 35 );
120
// for each bit append 0 or 1 to buffer
for ( int bit = 1; bit <= 32; bit++ ) {
123
// use displayMask to isolate bit and determine whether
// bit has value of 0 or 1
buffer.append(
( value & displayMask ) == 0 ? '0' : '1' );
128
// shift value one position to left
value <<= 1;
131
// append space to buffer every 8 bits
if ( bit % 8 == 0 )
buffer.append( ' ' ); }
136
Fig Demonstrating the bitwise shift operators (Part 4).

60. 137 return buffer.toString();}
139
// execute application
public static void main( String args[] ) {
BitShift application = new BitShift();
144
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); }
148
149 } // end class BitShift
Fig Demonstrating the bitwise shift operators (Part 5). Program Output

61. Fig. 20. 11 Demonstrating the bitwise shift operators (Part 6)
Fig Demonstrating the bitwise shift operators (Part 6). Program Output

62. 20.8 Bit Manipulation and the Bitwise Operator (cont.)

63. BitSet class
BitSet
Facilitates the creation and manipulation of bit sets
Represent set of boolean flags
Dynamically resizable

64. 1 // Fig. 20.13: BitSetTest.java
2 // Using a BitSet to demonstrate the Sieve of Eratosthenes. 3
4 // Java core packages
5 import java.awt.*;
6 import java.awt.event.*;
7 import java.util.*; 8
9 // Java extension packages
10 import javax.swing.*; 11
12 public class BitSetTest extends JFrame {
private BitSet sieve;
private JLabel statusLabel;
private JTextField inputField; 16
// set up GUI
public BitSetTest() {
super( "BitSets" ); 21
sieve = new BitSet( 1024 ); 23
Container container = getContentPane(); 25
statusLabel = new JLabel( "" );
container.add( statusLabel, BorderLayout.SOUTH ); 28
JPanel inputPanel = new JPanel(); 30
inputPanel.add( new JLabel(
"Enter a value from 2 to 1023" ) ); 33
// textfield for user to input a value from 2 to 1023
inputField = new JTextField( 10 );
Fig Demonstrating the Sieve of Eratosthenes using a BitSet. Line 22
Create bitset of 1024 bits

65. Use method set to turn on all bits in BitSet36
inputField.addActionListener( 38
new ActionListener() { 40
// determine whether value is prime number
public void actionPerformed( ActionEvent event ) {
int value = Integer.parseInt( inputField.getText() ); 45
if ( sieve.get( value ) )
statusLabel.setText(
value + " is a prime number" ); 49
else
statusLabel.setText( value +
" is not a prime number" ); } } ); 56
inputPanel.add( inputField );
container.add( inputPanel, BorderLayout.NORTH ); 59
JTextArea primesArea = new JTextArea(); 61
container.add( new JScrollPane( primesArea ),
BorderLayout.CENTER ); 64
// set all bits from 1 to 1023
int size = sieve.size(); 67
for ( int i = 2; i < size; i++ )
sieve.set( i ); 70
Fig Demonstrating the Sieve of Eratosthenes using a BitSet (Part 2). Lines 68-69
Use method set to turn on all bits in BitSet

66. Determine prime numbers
// perform Sieve of Eratosthenes
int finalBit = ( int ) Math.sqrt( sieve.size() ); 73
for ( int i = 2; i < finalBit; i++ ) 75
if ( sieve.get( i ) ) 77
for ( int j = 2 * i; j < size; j += i )
sieve.clear( j ); 80
// display prime numbers from 1 to 1023
int counter = 0; 83
for ( int i = 2; i < size; i++ ) 85
if ( sieve.get( i ) ) {
primesArea.append( String.valueOf( i ) );
primesArea.append( ++counter % 7 == 0 ? "\n" : "\t" ); } 90
setSize( 600, 450 );
setVisible( true ); } 94
// execute application
public static void main( String args[] ) {
BitSetTest application = new BitSetTest(); 99
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE ); }
103
104 } // end class BitSetTest
Determine prime numbers
Fig Demonstrating the Sieve of Eratosthenes using a BitSet (Part 3). Lines 72-79

67. Fig. 20.13 Demonstrating the Sieve of Eratosthenes using a BitSet (Part 4). Program Output