Unmodifiable Collections

The Collections API provides a set of static methods that create unmodifiable wrappers for collections. Unmodifiable wrappers throw UnsupportedOperationExceptions if attempts are made to modify the collection. Headers for these methods are listed in Fig. 19.23. Details about these methods are available at java.sun.com/j2se/5.0/docs/api/java/util/Collections.html. All these methods take a generic type and return an unmodifiable view of the generic type. For example, the following code creates an unmodifiable List (list2) that stores String objects:

 List< String > list1 = new ArrayList< String >();
 List< String > list2 = Collections.unmodifiableList( list1 );

Figure 19.23. Unmodifiable wrapper methods.

(This item is displayed on page 951 in the print version)

public static method headers

< T > Collection< T > unmodifiableCollection( Collection< T > c )

< T > List< T > unmodifiableList( List< T > aList )

< T > Set< T > unmodifiableSet( Set< T > s )

< T > SortedSet< T > unmodifiableSortedSet( SortedSet< T > s )

< K, V > Map< K, V > unmodifiableMap( Map< K, V > m )

< K, V > SortedMap< K, V > unmodifiableSortedMap( SortedMap< K, V > m )

Software Engineering Observation 19.5

You can use an unmodifiable wrapper to create a collection that offers read-only access to others, while allowing readwrite access to yourself. You do this simply by giving others a reference to the unmodifiable wrapper while retaining for yourself a reference to the original collection.

Introduction to Computers, the Internet and the World Wide Web

Introduction to Java Applications

Introduction to Classes and Objects

Control Statements: Part I

Control Statements: Part 2

Methods: A Deeper Look


Classes and Objects: A Deeper Look

Object-Oriented Programming: Inheritance

Object-Oriented Programming: Polymorphism

GUI Components: Part 1

Graphics and Java 2D™

Exception Handling

Files and Streams


Searching and Sorting

Data Structures



Introduction to Java Applets

Multimedia: Applets and Applications

GUI Components: Part 2



Accessing Databases with JDBC


JavaServer Pages (JSP)

Formatted Output

Strings, Characters and Regular Expressions

Appendix A. Operator Precedence Chart

Appendix B. ASCII Character Set

Appendix C. Keywords and Reserved Words

Appendix D. Primitive Types

Appendix E. (On CD) Number Systems

Appendix F. (On CD) Unicode®

Appendix G. Using the Java API Documentation

Appendix H. (On CD) Creating Documentation with javadoc

Appendix I. (On CD) Bit Manipulation

Appendix J. (On CD) ATM Case Study Code

Appendix K. (On CD) Labeled break and continue Statements

Appendix L. (On CD) UML 2: Additional Diagram Types

Appendix M. (On CD) Design Patterns

Appendix N. Using the Debugger

Inside Back Cover

Java(c) How to Program
Java How to Program (6th Edition) (How to Program (Deitel))
ISBN: 0131483986
EAN: 2147483647
Year: 2003
Pages: 615

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