4. Object Structures, Aliasing, and Encapsulation

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2. A simple structure of several objects::LinkedListheader:size: 3: Entryelement:next:previous:: Entryelement:next:previous:: Entryelement:next:previous:: Entryelement:next:previous:... ... ...3. More interesting object structures can e.g. befound in graphical user interfaces.13.05.13© A. Poetzsch-Heffter, TU Kaiserslautern4
Problems:• Structural integrity ( structural invariants)• Behavior and state of an object tightly dependson other objects.• „Multiple references“ to one object ( aliasing)Explanation: (Aliasing in OO programming)An object X is aliased if two or more variables holdreferences to X. A variable can be- an instance variable- a class or static variable (global variable)- a local variable of a method incarnation,including the implicit parameter this- a formal parameter- the result of a method invocation or herintermediate expression resultsOften such a variable is called an alias of X.Aliasing is called static if all involved variables areinstance or static variables, i.e. belong to the heap.Otherwise, it is called dynamic.13.05.13© A. Poetzsch-Heffter, TU Kaiserslautern5
Page 1 and 2: 4. Object Structures, Aliasing,and
Page 3: Examples:(Object structures)1. A ve
Page 7 and 8: Undesirable Aspects of Aliasing:1.
Page 9 and 10: Forms of Alias Creation:Capturing:
Page 11 and 12: General approaches to solve alias p
Page 13 and 14: Examples:1. Immutable class:(Immuta
Page 15 and 16: class NotImmutableList extends Immu
Page 17 and 18: 4. Immutable objects with varying I
Page 19 and 20: 4.3 Alias Control and Encapsulation
Page 21 and 22: Roles in Object Structures:• Inte
Page 23 and 24: 2. Representations (rep mode):• E
Page 25 and 26: Meaning of alias modes:• Alias mo
Page 27 and 28: Programming Discipline (simplified)
Page 29 and 30: Example:(Representation exposure)-
Page 31 and 32: 4.3.2 Type-based EncapsulationType
Page 33 and 34: Connection with type systems:• Ea
Page 35 and 36: Scenarios in which references are i
Page 37 and 38: Remark:• The behavior of anonymou
Page 39 and 40: Further Structuring Techniques:Diff
Page 41 and 42: Cluster:Let G be the undirected gra
Page 43 and 44: Ownership:Idea:• Introduce an own
Page 45: The ownership relation is a binary

4. Object Structures, Aliasing, and Encapsulation

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