method glossary
A
abstract A method with no body; a method signature followed by a semi-colon. alternative In a conditional statement, the optional sub-statement to be executed if the boolean test expression's value is false. applet A Java program capable of running embedded in a web browser or other specialized applet environment. Contrast application. application A Java program capable of running "standalone". Contrast applet. animacy A Java Thread that enables concurrent execution, e.g., of a self-animating object. See the chapter on Self-Animating Objects. animate object See self-animating object. array A structure for holding many Things of the same type. argument A value supplied to a method when it is invoked. During the execution of the method body, this value is named by the matching method parameter. arithmetic operator
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Glossary
An operator that computes one of the arithmetic functions. See the chapter on Expressions. assignment The association of a name with a value. See the chapter on Things, Types, and Names. Also the operator in such an assignment. See the chapter on Expressions. asterisk * Sometimes called "star". Used to delineate certain comments and as the multiplication operator.
B
backslash \ Used in character escapes. binary operator An operator that takes two operands. See the chapter on Expressions. binding See name binding. bit A single binary digit. bitwise operator An operator that computes a bit-by-bit function such as bitwise complement. See the chapter on Expressions. block A segment of code that begins with a { and ends with the matching }. See the section on Blocks in the chapter on Statements. body The body of a method, class, or interface, i.e., either a method body, a class body, or an interface body.
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boolean A true-or-false value. In Java, represented by the primitive type boolean and by the object type Boolean. See the sidebar on Java Primitive Types in the chapter on Things, Types, and Names. boolean expression An expression whose type is boolean. boot, boot up Start up (a computer or program). bottom-up design An approach to design that starts with the simplest, most concrete things in your system and proceeds by combining them. brace { or } Used to enclose bodies or blocks. bracket [ or ] Used in array expressions. bug An error in a program. Contrast feature.
C
call See invocation. call path The sequence of method invocation (instructions followed by a Thread) that led up to the currently executing method body. Unless execution exits abruptly, each of these invocations will return, one at a time, in this order, along the reverse of the call path, i.e., the return path. carriage return
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G~4
Glossary
One of two line-ending characters. (The other is line feed.) So named after an archaic device called a typewriter in whose early models the carriage (i.e., paper-bearing part) literally needed to be returned to the other side of the typewriter at the end of each line. case-sensitive Distinguishing between upper and lower case letters. cast expression An expression involving a type and an operand whose value is the same as its operand but whose type is the type supplied. Contrast coercion. catastrophic failure An exceptional circumstance so incapacitating that your program cannot hope to prevent or deal with it. At this point, the only hope is in recovery.
catch
statement
A particular kind of Java statement, typically used with exceptions, that receives a thrown object. See the chapter on Exceptions. character A single letter, digit, piece of punctuation, or piece of whitespace. In Java, represented by the primitive type char, using unicode notation, and occupying sixteen bits, and by the object type Char. See the sidebar on Java Primitive Types in the chapter on Things, Types, and Names. character escape A special sequence indicating a character other than by typing it directly. Especially useful for non-printing characters, such as carriage return. class A (user-definable) type from which new objects can be made. See the chapter on Classes and Objects. class body The portion of a class definition containing the class's members. The portion of a class definition enclosed by { }. See the chapter on Classes and Objects and the Java Chart on Classes.
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class object The object representing the class itself, i.e., the factory. Itself an instance of class java.lang.Class. code An excerpt from a program. coercion Treating an object of one type as though it were of another type. Contrast cast. See the chapter on Expressions. comment Text embedded in a program in such a way that the Java compiler ignores it. Intended to make it easier for people to read and understand the code. comparator An operator in an expression of boolean type. compiler The utility that transforms your Java code into something that can be run on a Java virtual machine. compount assignment A shorthand assignment operator (or expression) that also involves an arithmetic or logical operation. concatenation The gluing together of two strings. condition In a conditional statement, the boolean expression whose value governs whether the consequent or the alternative is executed. conditional A compound statement whose execution depends on the evaluation of a boolean expression. Consists of a condition, a consequent, and an optional
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G~6
Glossary
alternative. conjunction The logical operator && (and). concurrent Literally or conceptually at the same time. consequent In a conditional statement, the sub-statement to be executed if the boolean test expression's value is true. console See Java console. constant A name associated with an unchanging value. Typically declared final. constructor The code which specifies how to make an instance of a class. Its name matches the name of the class. A constructor is a class member. See the chapter on Classes and Objects.
D
data Values, as opposed to executable code. Things that might be associated with names such as variables, parameters, or fields. See also state. data repository A kind of object whose primary purpose is to store data. See the chapter on Designing with Objects. debug To attempt to eliminate bugs from your program. declaration
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A statement associating a name with a type. Once the name has been declared, it can be used to refer to Things of the associated type. See the chapter on Things, Types, and Names. default value The value associated with a name that has been declared but not assigned a(n initial) value. See the sidebar on Default Initialization in the chapter on Things, Types, and Names. default visibility Also called package visibility. The visibility level of an unmodified interface, class, method, field, or constructor. Visible to only within the package. definition A statement that both declares and initializes a name. See the chapter on Things, Types, and Names. design The process of figuring out what your program should do and how it should accomplish it. disjunction The logical operator || (or). dot See period. double precision floating point A representation for rational numbers (and an approximation for real numbers) that uses 64 bits of storage. In Java, implemented by the primitive type double. See floating point. down cast A cast from superclass to subclass. May be invalid; should be guarded.
E
embedded
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Glossary
The property of being in an environment (or system) and interacting with it. entity A member of the community. A conceptual unit consisting of an object or set of objects that is (implicitly or explicitly) persistent and that interacts with other entities. environment Where an entity is embedded. What the entity interacts with. error checking Code (often a conditional statement) designed to catch illegal values or other potential problems, and to correct them, before or as they arise. A way to avoid bugs in your program. An important part of design. evaluate To compute the value of an expression. event 1. Something that happens. 2. A special kind of object used in event-driven programming to record the occurrence of a particular event (in the conventional sense). See the chapters on Event-Driven Programming and Event Delegation. event-driven programming A style of programming in which an implicit (often, system-provided) control loop activates event handler methods when a relevant event occurs. See the chapters on Event-Driven Programming and Event Delegation. event handler In event-driven programming, a method that is called when a relevant event occurs. See the chapters on Event-Driven Programming and Event Delegation. exit condition The condition under which the repeated execution of a loop stops. Formally called the termination condition for the loop.
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exception A special kind of Java object used to indicate an exceptional circumstance. Typically used in conjunction with throw and catch statements. See the chapter on Exceptions. execute To follow the instructions corresponding to a statement or program. expression A piece of Java code with a type and a value, capable of being evaluated. Contrast statement. See the chapter on Expressions. extend To reuse the implementation supplied by a superclass through inheritance.
F
factory A class, metaphorically, for its instances. feature 1. A deliberately designed and generally beneficial aspect of a program. 2. post hoc. A bug, when discovered by a user after it's too late to fix it. field A data member of a class, i.e., a name associated with each instance of a class (if not static) or with the class object itself (if static). See the chapter on Classes and Objects. field access An expression requiring an object and a field name. Its type is the declared type of the field and whose value is the value currently associated with that field. floating point A representation for rational numbers (and an approximation for real
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Glossary
numbers) that uses 32 bits of storage. In Java, implemented by the primitive type float. Contrast double precision floating point. footprint See method footprint.
G
getter, getter method A method that exists solely to provide read access to a field. Formally called a selector. global variable A term with no meaning in Java. graphical user interface A user interface that makes use of windows, icons, mouse, etc., and is typically implemented in an event-driven style. Sometimes abbreviated GUI. guard expression A test that prevents execution of a potentially dangerous statement. GUI An acronym for graphical user interface.
H
hyphen - Used as the unary and binary subtraction operator and to indicate negative numbers.
I
identifier The formal term for a name. idiot proofing
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A not very tactful name for error checking, especially as concerns interaction with the user.
if, if/else
Java's conditional statement. implementor The 1. person or 2. entity that provides the implementation for an interface or contract. implementation Executable code. Also "how to". incremental program design The design-build-test-design cycle in which every attempt is made to keep the program working at all times and to make only minor modifications between tests. inheritance The process by which one class shares the definition and implementation provided by another. Uses the Java keyword extends. See the chapter on Inheritance. initialization The assignment of an initial value to a name or, by extension, to an object's fields. instance An object created from a class, whose type is that class. See the chapter on Classes and Objects. instantiate To create an instance from a class, typically through the use of a constructor (and new). instruction follower The thing that executes statements. In Java, a Thread.
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G~12
Glossary
instructions Code, generally statements, explaining how to do something. Followed step by step by an instruction follower. integer type In Java, one of byte, short, int, long, char, or boolean. Expressions of these (and only these) types may be used as the test expression of a switch statement. interface 1. The common region of contact between two or more entities. 2. (Java) A formal statement of method signatures and constants defining a type and constraining the behavior of objects implementing that interface. See the chapter on Interfaces. interface body The portion of an interface definition containing the interface's members. The portion of an interface definition enclosed by { }. invocation To call a method, i.e., execute its body, passing arguments to be associated with the method's parameters.
J
Java console A place in every Java environment from which standard input is read and to which standard output is written. I/O to the Java console is provided by cs101.util.Console, java.lang.System.in, and java.lang.System.out. jelly An exceedingly sticky concoction made from the juice of a fruit, often a grape, ideally purple. See also peanut butter.
K
keyword
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A word with special meaning in Java. All Java keywords are reserved, i.e., cannot be used as Java names.
L
label name A name capable of referring to something of an object type, i.e., anything not of a primitive type. See the chapter on Things, Types, and Names. left-hand side In an assignment, the expression representing the shoebox or label to which the value is assigned. literal A Java expression to be read literally, i.e., at face value. Only the primitive types plus strings have corresponding literal expressions. See the sidebar on Java Primitive Types in the chapter on Things, Types, and Names. local Another term for a variable. Short for local variable. local variable The formal term for a variable. logical operator An operator that computes an arithmetic function such as conjunction or disjunction. See the chapter on Expressions. loop A construct by which a sequence of statements is executed repeatedly, typically until some exit condition is met.
M
member A constructor, field, method or of a class. Alternately, a (static) field or (abstract) method of an interface. Also member (inner) classes or interfaces. See the chapter on Classes and Objects.
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Glossary
method An executable class member. Consists of a signature plus a body (unless abstract). When a method is invoked on an argument list, the body is executed with each of the method's parameter names bound to its corresponding argument. method body The portion of a method that contains executable statements. When a method is invoked (on a list of arguments), its body is executed within the scope of the parameter bindings, i.e., with the parameter names bound to the corresponding arguments. method footprint The name plus the ordered list of parameter types of a method. An object may have at most one method with any particular footprint. Contrast method signature. See the chapter on Interfaces. method invocation See invocation. method overriding When a subclass redefines a method or field that would otherwise be inherited from its superclass. method overloading When one object has two or more methods with the same name (but different footprints), typically performing different functions. method signature The specification of a method's name, ordered list of parameter types, return type, and exceptions, possibly including modifiers. Contrast method footprint. See the chapter on Interfaces. modifier A formal Java term such as abstract, final, public, static, synchronized, etc., which is used in the definition of a class, interface, or member. See the Java Charts for details.
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mutator The formal name for a setter method.
N
name A Java expression that refers to a particular object or value. Examples include variables, parameters, fields, class names, and interface names. Every name has an associated type (fixed when the name is declared). Within its scope, the name is generally bound to a value (of the appropriate type). See the chapter on Things, Types, and Names. name binding The association of a name with a value, typically through assignment or through parameter binding during method invocation. The details of this association depend on whether the name is a shoebox name or a label name, i.e., of primitive or object type. no-args Taking no arguments or, more properly, having no parameters.
null
A Java keyword. The non-value with which an unbound label name is associated. null character The character with unicode number 0. Not to be confused with the non-value null.
O
object A non-primitive, non-null Java Thing. An instance of (a subclass of) java.lang.Object. object type In Java, any type other than one of the eight primitive types. All object types are named by label names.
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Glossary
operand One sub-expression of an operator expression. See the chapter on Expressions. operator The part of an operator expression that determines the particular relationship of the operands to the expression's value. See the chapter on Expressions. operator expression An expression involving an operator (e.g., +) and one or more operands. Typically, the value of the expression is a particular function of the operands, with the operator specifying what function. See the chapter on Expressions. overriding See method overriding. overloading See method overloading.
P
package 1. A named group of Java interface and class definitions. 2. The default visibility level of an unmodified interface, class, method, field, or constructor. Visible only within the package(1). paper An archaic but amazingly persistent storage medium made of wood pulp. Reported continually over the last half-century to be destined for imminent obsolesence with the incipient advent of the paperless office. Sometimes used with a typewriter. parameter A name whose scope is a single invocation of the method to which it belongs. Declared in the method signature. When the method is invoked on a list of arguments, each parameter is bound to the corresponding argument prior to (and with scope over) the execution of the method body.
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parameter binding The form of name binding that occurs when a method is invoked on a list of arguments. Each of the method's parameters is bound to the corresponding argument, i.e., the first parameter to the first argument, etc. peanut butter A gooey brown paste made by grinding up a certain legume, often consumed with jelly between two slices of very bland white bread. period . Sometimes also called "dot". Used in method invocation and field access expressions, package naming, and as a decimal point. persistent Existing even when not currently the subject of the coder's or computer's attention. pointer A term with no meaning in Java. postfix Coming after. prefix Prior to. primitive type In Java, one of byte, short, int, long, float, double, char, or boolean. All primitive types are named by shoebox names. See the sidebar on Java Primitive Types in the chapter on Things, Types, and Names.
private
A Java keyword. A class or interface member declared private is visible only within the body of its defining class or interface. program n. A collection of executable code. The how-to instructions that a computer
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Glossary
follows. v. To compose a program. See also incremental program design, debug. programmer A person who develops (designs, writes, debugs, modifies) a program. programming language A language in which one writes a program. For the purposes of this book, Java.
protected
A Java keyword. A class or interface member declared protected is visible within its package and within any class (or interface) that extends (or implements) its containing class (or interface).
public
A Java keyword. An interface, class, method, field, or constructor declared public is visible everywhere.
Q R
read, read access Interacting with a name by obtaining its associated value, or with an object by reading the value(s) of one or more of its fields. recipe The instructions for how to do something. A class is a recipe for the behavior of its instances. A constructor is the recipe for how to make an instance of its class. recovery Also recovering from error. What a program ought to do after something has gone wrong; patch things up as well as possible and move on. If things are disasterous enough (e.g., after a catastrophic failure), this can be a significant task. It is facillitated by design that anticipates the need for eventual recovery.
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reference type The formal term for the types named by a label name. reserved word A word that cannot be used as an identifier in Java, typically because it is a keyword. resource library A class that exists to hold methods that don't logically belong to any particular object, or other (typically system-wide) resources. Typically not an instantiable class. See the chapter on Designing with Objects. return A statement whose execution causes normal termination of the execution of a method body. If the return statement contains an expression, its type must match the return type of the method. In this case, the expression is evaluated prior to exiting the method body and the value of this expression is the return value of the method invocation. return path See call path. return type The type of the value returned by a method invocation. The first item in a method declaration. return value The value returned by a method invocation. rule A proto-method. Consists of a specification and a body. See the chapter on Statements and Rules. rule body The set of statements detailing how a rule is to be accomplished. A protomethod body. See the chapter on Statements and Rules.
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Glossary
rule specification The information needed and provided by a rule. A proto-signature. See the chapter on Statements and Rules.
S
scope The expanse of code within which a name has meaning, i.e., is a valid expression. See the note on Scoping in the chapter on Expressions. Not quite. selector The formal name for a getter method. self-animating object An object or entity with its own animacy, i.e., one that runs concurrently and persistently. See the chapter on Self-Animating Objects. setter, setter method A method that exists solely to provide write access to a field, i.e., to change its value. Formally called a mutator. shared reference A situation in which two label names refer to the same object. shoebox name A name cap...