This page contains a list of vocabulary words used or defined in class. You should be familiar with the meaning of these terms. If you hear an unfamiliar word used in class, please nominate it for inclusion in this list.
Relating to Variables
- Type: A designation applied to each variable describing how it is stored in memory, and also what operations are permissible with it.
- Primitive Type: One of eight simple types in Java that are stored directly, not by reference. The eight primitive types are
byte, short, int, long, float, double, boolean, and char.
- Reference Type: All other types in Java. Includes classes and arrays. These types are represented as a reference (i.e., memory address) to a data storage area allocated on the heap (one of the areas of memory available to a program).
- Qualifier: A word appearing in a field definition before the type, that modifies the behavior of the field in some way. It might change the access (e.g.,
public or private) or the allocation (e.g., static) or the mutability of the value (e.g., final).
- Declaration: A piece of Java code that specifies the type of a variable, possibly with one or more qualifiers. Sometimes combined in a single line with assignment and/or allocation, but not always. Example:
int x;
- Assignment: Putting a value into a variable. Example:
x = 7;
- Allocation: Creation of space on the heap to store the data for some reference type; typically requires use of the keyword new. Automatically triggers execution of a constructor to fill in the data.
Relating to Methods
- Method Definition: The entire piece of code that describes a method.
- Call signature: The unique identifying pattern formed by the return type of a method, its name, and the types of its parameters/arguments. The first line of the method definition shows its call signature.
- Method Body: The part of the method definition that describes the steps to be executed. It appears inside curly brackets following the method name and parameter list.
- Method Call (or Invocation): A java command that causes a method to start executing. The call must provide values (called arguments) for each of the parameters required by the method.
- Parameter: A piece of information that must be provided to a method in order for it to run. It is listed in the first line of the method definition, within the parentheses after the method name. Within the method body the parameter acts the same as a local variable.
- Argument: A value provided when a method is called, that is assigned to one of the method’s parameters.
- Local Variable: A variable that is declared within the body of a method. It ceases to exist when the method finishes executing. (If the method is called again, the local variable is created again, but there is no continuity between the old one and the new.)
Relating to Classes
- Class: A unit of code representing some concept, task, or other entity. The basic unit of a Java program.
- Field: A piece of data stored by a class.
- Method: A piece of code associated with a class that can be executed, like a function.
- Member: This term refers to both fields and/or methods.
- Instance (of a class): One particular copy of the memory structure defined by a class, consisting of an area of memory with storage space for all of its fields. Created by calling one of the class’s constructors using the
new keyword. A program may create any number of instances of a class.
- Object: An instance of any class is also called an object.
- Constructor: A special method, whose job is to initialize all the class’s fields.
- Accessor: A method whose job is to report the value of one of the class’s fields.
- Manipulator: A method whose job is to alter the value of one of the class’s fields.
Relating to Inheritance
- Inheritance: A technique for writing more efficient code, whereby the fields and methods of one class (the parent or superclass) are transferred to another class (the child or subclass) as it is defined.
- Subclass: A class that inherits members from another.
- Superclass: A class whose members are inherited by some other class.
- Override: When an inherited method is replaced by a new definition, the old method is said to have been overridden.
- Specialize: A subclass is said to specialize its parent class.