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M250 Java book 1
Open Uni M250 Object Oriented Java Programming Book 1 (units 1-5)
| Term | Definition |
|---|---|
| access modifier | A keyword that controls the visibility of class members to objects of other classes. The modifiers 'private' and 'public' are the most frequently used access modifiers. |
| accessor message | Another name for a 'getter message'. A message that returns as its message answer the value of one of the receiver's attributes. |
| accessor method | Another name for a 'getter method'. A method whose purpose is to return the value of one of an object's attributes as its message answer. |
| actual argument | An actual argument is a value used in a message that is copied to a formal argument for use inside the corresponding method. Actual arguments must be of a compatible type with their corresponding formal arguments. |
| application domain | (also: problem domain)The collection of real-world entities within the application area that exhibit the behaviours that the required system has to model. |
| assignment | Assignment is the process that results in variable left of assignment operator receiving a copy of value right of assignment operator. Value may be a primitive value or a reference to an object. If right-hand value is an expression it is evaluated first. |
| assignment operator | An operator (=) used to assign a value to a variable in an assignment statement. |
| assignment statement | A statement that assigns a particular value to a variable. |
| attribute | Some property or characteristics of an object that can be accessed using a getter method. Attributes are generally implemented by instance variables. |
| attribute value | The current value of an attribute, often the same as an instance variable value, but possibly computed using instance variables. |
| automatic type conversion | Where the Java compiler converts value of some type to another type without need for explicit conversion of type on part of the programmer. Can occur in assignment statement when compatible type on right hand is converted to type of variable on left hand. |
| behaviour | A term used to describe the way in which an object behaves in response to the messages in its protocol. |
| binary digit | Either of the two digits 0 and 1 in the binary number system. Binary digits are used for the internal representation of numbers, characters and instructions. The binary digit is the smallest unit of storage. |
| binary operator | An operator that has two operands. |
| bit | An abbreviation of binary digit. |
| body | Another word for a statement block; for example: the body of a while loop is a statement block. |
| Boolean condition | A Boolean expression used to control the conditional execution of a statement block. |
| Boolean expression | An expression that evaluates to either true or false. |
| Boolean operator | An operator used to combine simple Boolean expressions to form more complex Boolean expressions, which in turn can be combined with other Boolean expressions. They are also known as logical operators. |
| bytecode | Bytecode is the intermediate code produced by the Java compiler in a bytecode file. Bytecode is portable because a JVM understands bytecode and converts it into the machine code required for that particular computer. These instructions are a byte in size. |
| casting | The prefixing of a value with the name of a type in parentheses in order to convert a copy of that value into a different type. |
| class | A class is like a blueprint for the creation of objects and ensures that all its instances have the same instance variables and behave in response to messages in an identical manner. |
| class header | The line of code in a class definition that provides information about a class such as its name and access modifier. A class header must include the keyword class. |
| class method | These are methods defined by the class, that can be executed irrespective of whether any instances of the class have been created. A class method is executed as a result of an invocation. They are specified by including the static keyword in the header. |
| comment | A comment is a piece of text in program code to assist human readers in understanding the code, and which the compiler ignores. Multi-line comments: /* and */. End of line comments begin with // and finish at end of line. Javadoc comments: /** and */ |
| comparison operators | A set of operators used for comparing values of expressions, including ==, > and < |
| compiler | A program that first checks that the source code written in a high-level language is syntactically correct. If the check is successful the compiler translates the source code into bytecode or machine code. The compiler translates source code into bytecode |
| compound expression | An expression built up using other sub-expressions, for example: (3 + 2) * (6 - 3) |
| concatenation | The joining of two strings. The string concatenation operator is + |
| conditional selection | The use of if statements to select and execute alternative statement blocks based upon the value of a Boolean condition. |
| constructor | A programming construct, similar to a method, used to initialise a newly created object. |
| convention | A commonly followed rule for implementing some feature of a software system that is not enforced by the language used, compiler, or platform on which the software is used. |
| data hiding | Where an object is treated as a black box, with access to the encapsulated date (instance variables) being possible only through a limited set of methods. |
| declaration | A statement in which memory is reserved for a variable of some type that is formed by writing the type of the variable followed by some name (its identifier) |
| dialogue box | A type of window with buttons through which users can be given information by a program or provide information to a program on request. |
| direct access | Accessing an instance variable using its name, rather than using a getter method. |
| dynamic compilation | A compilation technique generating real machine code from bytecode. A chuck of bytecode is compiled into machine code just prior to being executed. The real machine code is retained so that translation doesn't have to be repeated for subsequent execution. |
| encapsulation | Encapsulation is the parcelling up of information and behaviour into reusable component. Objects allow you to encapsulate data by incorporating into a single entity (object) both the data (instance variables) and behaviour (methods) defined for that data. |
| escape character | A character used to mark the start of an escape sequence in a string. In Java this is the \ (backslash) character. |
| escape sequence | A sequence of characters beginning with a special escape character, that allows subsequent characters to take on a different meaning for the compiler. |
| evaluate | To find the value of something. |
| comparison operators | A set of operators used for comparing values of expressions, including ==, > and < |
| compiler | A program that first checks that the source code written in a high-level language is syntactically correct. If the check is successful the compiler translates the source code into bytecode or machine code. The compiler translates source code into bytecode |
| compound expression | An expression built up using other sub-expressions, for example: (3 + 2) * (6 - 3) |
| concatenation | The joining of two strings. The string concatenation operator is + |
| conditional selection | The use of if statements to select and execute alternative statement blocks based upon the value of a Boolean condition. |
| constructor | A programming construct, similar to a method, used to initialise a newly created object. |
| convention | A commonly followed rule for implementing some feature of a software system that is not enforced by the language used, compiler, or platform on which the software is used. |
| data hiding | Where an object is treated as a black box, with access to the encapsulated date (instance variables) being possible only through a limited set of methods. |
| declaration | A statement in which memory is reserved for a variable of some type that is formed by writing the type of the variable followed by some name (its identifier) |
| dialogue box | A type of window with buttons through which users can be given information by a program or provide information to a program on request. |
| direct access | Accessing an instance variable using its name, rather than using a getter method. |
| dynamic compilation | A compilation technique generating real machine code from bytecode. A chuck of bytecode is compiled into machine code just prior to being executed. The real machine code is retained so that translation doesn't have to be repeated for subsequent execution. |
| encapsulation | Encapsulation is the parcelling up of information and behaviour into reusable component. Objects allow you to encapsulate data by incorporating into a single entity (object) both the data (instance variables) and behaviour (methods) defined for that data. |
| escape character | A character used to mark the start of an escape sequence in a string. In Java this is the \ (backslash) character. |
| escape sequence | A sequence of characters beginning with a special escape character, that allows subsequent characters to take on a different meaning for the compiler. |
| evaluate | To find the value of something. |
| expression | Code that evaluates to a single value. Expressions can be formed from literals, variables, operators and messages. |
| floating-point type | A type capable of representing a decimal number (to a restricted level of accuracy) |
| for statement | A statement following a statement block to be repeatedly executed according to the value of a loop control variable and a Boolean condition whose value is dependent on the loop control variable. for loops typically used for fixed number of iterations. |
| formal argument | A typed identifier used in a method signature between parentheses to stand for a value (an actual argument) that is passed into the method body by a message. |
| garbage collection | The process of destroying objects that have become unreachable because they are no longer referenced by variables, in order to reclaim their space in memory. This process is automatic. |
| getter message | A message that returns as its message answer the value of one of the receiver's attributes. |
| getter method | A method whose purpose is to return the value of one of an object's attributes as its message answer. |
| graphical representation | A visible representation of a software object that, by definition, is invisible. |
| helper method | A method whose purpose is to do some internal work of an object and which therefore should have private access so that it cannot be used by objects of other classes. |
| high-level language | A language whose structure reflects the requirements of the problem, rather than the facilities provided by the hardware. It enables a software solution to a problem, or simulation of an aspect of reality, to be expressed in a hardware independent manner. |
| identifier | The name given to a variable, method or formal argument. |
| if statement | A programming construct whereby one or more statement blocks are conditionally executed, according to whether a Boolean condition evaluates to true or false. |
| inheritance | The process by which a subclass can make use of members of its superclass, such as instance variables and methods, without having to define them itself. |
| inspector | An inspector is a tool used in M250 to look at the value held by a variable declared in the OUWorkspace |
| instance | An object that belongs to a given class is described as an instance of that class. |
| instance method | Code that is executed as the result of a message being sent to an object. |
| instance variable | A variable whose identifier and type is common to all the instances of a class, but whose value is specific to each instance. Each instance variable either contains a reference to an object or contains a value of some primitive type. |
| integrated development environment (IDE) | A software tool that supports the development, compilation and execution of computer programs. BlueJ is an example of an IDE that supports the development of programs in Java. |
| interpreter | A program that translates statements from a high-level language, such as Java, to a machine code language, and executes the machine code. |
| invocation | Executing code in a method. Class (static) methods are invoked directly on a class, whereas instance methods are invoked by sending messages to objects. |
| iteration | Also referred to as repetition. The repeated execution of a statement block for as long as some Boolean condition evaluates to true. |
| Java edition | A category of Java targeted at a particular platform or domain, such as desktop systems or mobile devices. |
| Java version | A release of an edition of Java. |
| Javadoc | A programming tool that comes with Java. The Javadoc tool picks up information from specially formatted comments and other parts of the class code such as the constructor and the method headers. These are used to create HTML file which describes the class |
| keyword | A Java keyword is a word reserved for use in the language. Keywords cannot be used as variable identifiers. |
| lazy evaluation | A type of evaluation used in compound Boolean expressions involving the && and || operators whereby the second operand is evaluated only when it is necessary to do so in order to determine the truth value of the whole expression. |
| literal | A textual representation of a primitive value or object. |
| local variables | A variable that is declared inside a statement block, such as inside a method body, or for statement, or, in the case of M250, the OUWorkspace. The scope of such a variable is restricted to the statement block in which it is declared. |
| logical operator | An operator whose operands are Boolean values and which evaluates to a Boolean value. |
| loop | In programming, a loop is a sequence of statements that is continually repeated until some Boolean condition is reached |
| loop control variable | A variable used to regulate the number of times a loop such as a for statement or while statement is executed; such a variable is typically declared inside a for loop's header or before a while loop. |
| low-level language | A language written for direct programming of a computer's hardware. Each type of computer hardware needs its own low-level language. |
| member | Instance variables, instance methods, class variables and class methods can all be described as being members of a particular class. |
| message | A message is a request for an object to do something. |
| message answer | When a message is sent to an object, then, depending on what the message is, a message answer may be returned. A message answer is a value or an object; it is not a message. |
| message expression | A message-send that evaluates to some value; i.e. the message returns a message answer. |
| message name | The name of a message, including the following parentheses, but excluding any arguments. |
| message-send | The code that sends a message to an object. |
| method | The code that is invoked by the Java Virtual Machine at run-time when an object receives a message. |
| method body | That part of a method enclosed by braces that follows the method header. The body of a method is an example of a statement block. |
| method header | A method header consists of an access modifier, a return value and a name followed by any formal argument names enclosed in parentheses. |
| method invocation | At run-time, selecting and executing a method when an object receives a message. |
| method signature | The name of the method together with the parentheses and the types of any arguments. |
| microworld | A computer-based simulation with opportunities for manipulation of content and practice of skills. |
| modal (dialogue box) | A dialogue box that will not allow you to interact with another part of the program until you have responded to it by clicking one of the buttons presented. All the dialogue boxes provided by the class OUDialog are modal dialogue boxes. |
| model (verb) | To simulate an entity in the problem domain using software. |
| mutator message | Another name for a setter message. |
| mutator method | Another name for a setter method. |
| new | A keyword used to create an object - used in conjunction with a constructor. |
| object | An instance of a class. An object has both state, represented by its attributes, and behaviour, its responses to the the set of messages it understands (its protocol). An object models a part of a solution to a software problem. |
| object diagram | An object diagram represents an object. It shows the class of the object, its state in terms of attribute values and its protocol. |
| object initialisation | The state of an object when it is first created depends on its initialisation, a process whereby its instance variables are set to known values. This is usually carried out by the constructor in the class. |
| object-oriented programming | An approach to programming in which a software problem is modelled using classes of objects that can achieve a solution by sending messages to one another. |
| object-oriented technology | The technology associated with viewing software as being made up of objects. |
| operand | An expression provided to an operator. A binary operator such as + has a left-hand operand and a right-hand operand. |
| operating system (OS) | The software that manages the resources of a computer, including controlling input and output, allocating system resources, managing storage space, maintaining security and detecting equipment failure. |
| operator | A symbol used as a function, that is, it has one or more values it operates on and returns a value. |
| overloading | A method is said to be overloaded when there are other methods, defined in the same class, or inherited from some superclass, with the same name but a different method signature. |
| parameter | A synonym for argument. |
| peripheral device | Any part of the computer that is not part of the essential computer, such as a mouse, keyboard or flash drive. |
| postfix operator | An operator that appears after its operand(s) |
| precedence rules | Rules for determining the order in which various operators are evaluated in a complex expression. |
| primitive data type | A set of values together with operations that can be performed on them. The primitive data types in Java provide a set of basic building blocks from which all of the more complex types of data can be built. Primitive data types: int, char and Boolean |
| primitive type variable | A variable declared to hold a value of the declared or compatible primitive data type. Less formally we refer to a primitive variable. |
| primitive value | A value of some primitive type (int, Boolean or char values) |
| private | An access modifier that restricts access to a class member to objects of the class to which it belongs. |
| private protocol | The part of the protocol of a class or object that is inaccessible from a context outside of the class itself. |
| problem domain | The collection of real-world entities within the application area that exhibit the behaviours that the required system has to model. |
| procedural programming | An approach to programming in which a problem is broken down into smaller, simpler procedures, often incorporating global data structures. |
| program | A software solution to a problem, typically on a small scale. |
| protocol | The set of messages an object understands. |
| public | An access modifier applied to a class member that allows all classes of objects to have access. |
| public protocol | The part of the protocol of a class or object that is accessible from outside of the class itself. |
| receiver | The object to which a message is sent. |
| reference type variable | A variable declared to hold a reference to an object of the declared type (or a compatible type). Less formally we refer to a reference variable. |
| return type | The type of value returned by a method. |
| scope | The scope of a variable describes the areas of program code from which the variable may be used. The scope of a local variable is from the point where it is declared to the end of its enclosing statement block. |
| selection | A technique by which a statement or statement block is executed subject to some Boolean condition. An if statement is used to perform selection in Java. |
| sequence diagram | A diagram that depicts the interactions required between objects to carry out a particular task; this collaboration is shown in the form of messages and message answers. |
| setter message | A message that sets the value of one of a receiver's attributes. |
| setter method | A method whose purpose is to assign a new value to an instance variable. |
| short-circuit evaluation | another name for lazy evaluation |
| software | A general term for all programs that can be run on a desktop computer or another hardware platform, such as a mobile phone. |
| software component | A piece of software that can be readily combined with other components to construct more complex software. |
| source code | Program text expressed in a high-level programming language. |
| state | The values of the attributes of an object constitute its state. The state of an object can vary over time as the values of its attributes change. |
| statement | A statement represents a single instruction for the compiler to translate into bytecode. In Java most statements end with a semicolon. |
| statement block | A statement or sequence of statements 'bundled together' for use in a particular context. Any sequence of statements can be turned into a block by enclosing it in braces (curly brackets). |
| static | A Java keyword that defines a variable or method as belonging to a class rather than its instances |
| string | A sequence of characters enclosed in quotation marks; an object of type String. |
| strong typing | Programming language feat that requires variables to have declared type and enforces rules on ways in which those types can be used, incl types of values can be assigned to variables of those types and what operators values of those types can be used with |
| subclass | A subclass is a class defined in terms of an existing class (its superclass). Instances of a subclass inherit attributes and protocol from the superclass, but may define additional attributes and messages. |
| superclass | If B is a subclass of A, then A is the superclass of B. In Java programming a subclass has only one direct superclass. |
| syntax | The syntax of a programming language is the set of rules governing the structure of the language, including its valid symbols, expressions and structures. |
| this | An expression used within a method or constructor to reference the object executing the method or constructor. |
| unary operator | An operator that has just one operand. |
| variable | A named 'chunk' or block of the computer's memory which can hold either a value of some primitive type or a reference to an object. |
| variable initialisation | The process of assigning a variable a value for the first time. |
| variable reference diagram | A diagram showing the relationships between reference variables, objects and their instance variables. Object protocol is not included. |
| virtual machine (VM) | A layer of software that simulates a computer capable of interpreting. |
| void | A keyword used in Java to indicate that a method does not return a value. |
| while statement | A loop that allows a statement block to be repeatedly executed depending on the value of some Boolean condition. while loops are typically used to repeat code when the number of iterations cannot be determined in advance. |
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Annelien
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