Claim Academy Java Week 2

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abstract

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A Java keyword used in a class definition to specify that a class is not to be instantiated, but rather inherited by other classes. An abstract class can have abstract methods that are not implemented in the abstract class, but in subclasses.

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abstract class

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A class that contains one or more abstract methods, and therefore can never be instantiated. Abstract classes are defined so that other classes can extend them and make them concrete by implementing the abstract methods.

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abstract method

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A method that has no implementation.

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API

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Application Programming Interface. The specification of how a programmer writing an application accesses the behavior and state of classes and objects.

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bitwise operator

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An operator that manipulates the bits of one or more of its operands individually and in parallel. Examples include the binary logical operators (&, |, ^), the binary shift operators (<<, >>, >>>) and the unary one's complement operator (~).

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casting

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Explicit conversion from one data type to another.

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catch

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A Java keyword used to declare a block of statements to be executed in the event that a Java exception, or run time error, occurs in a preceding try block.

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compilation unit

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The smallest unit of source code that can be compiled. In the current implementation of the Java platform, the compilation unit is a file.

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declaration

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A statement that establishes an identifier and associates attributes with it, without necessarily reserving its storage (for data) or providing the implementation (for methods). See also definition.

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default

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A Java keyword optionally used after all case conditions in a switch statement. If all case conditions are not matched by the value of the switch variable, the default keyword will be executed.

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definition

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A declaration that reserves storage (for data) or provides implementation (for methods). See also declaration.

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derived from

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Class X is "derived from" class Y if class X extends class Y. See also subclass, superclass.

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exception

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An event during program execution that prevents the program from continuing normally; generally, an error. The Java programming language supports exceptions with the try, catch, and throw keywords. See also exception handler.

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exception handler

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A block of code that reacts to a specific type of exception. If the exception is for an error that the program can recover from, the program can resume executing after the exception handler has executed.

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garbage collection

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The automatic detection and freeing of memory that is no longer in use. The Java runtime system performs garbage collection so that programmers never explicitly free objects.

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GUI

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Graphical User Interface. Refers to the techniques involved in using graphics, along with a keyboard and a mouse, to provide an easy-to-use interface to some program.

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hierarchy

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A classification of relationships in which each item except the top one (known as the root) is a specialized form of the item above it. Each item can have one or more items below it in the hierarchy. In the Java class hierarchy, the root is the Object class.

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instanceof

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A two-argument Java keyword that tests whether the runtime type of its first argument is assignment compatible with its second argument.

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interface

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A Java keyword used to define a collection of method definitions and constant values. It can later be implemented by classes that define this interface with the "implements" keyword.

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JAR

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JAR (Java Archive) is a platform-independent file format that aggregates many files into one. Multiple applets written in the Java programming language, and their requisite components (.class files, images, sounds and other resource files) can be bundled in a JAR file and subsequently downloaded to a browser in a single HTTP transaction. It also supports file compression and digital signatures.

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process

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A virtual address space containing one or more threads.

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property

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Characteristics of an object that users can set, such as the color of a window.

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root

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In a hierarchy of items, the one item from which all other items are descended. The root item has nothing above it in the hierarchy. See also hierarchy, class, package.

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stream

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A stream is simply a byte-stream of data that is sent from a sender to a receiver. There are two basic categories, so the java.io package includes two abstract classes (InputStream and OutputStream).

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subarray

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An array that is inside another array.

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subclass

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A class that is derived from a particular class, perhaps with one or more classes in between. See also superclass, supertype.

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subtype

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If type X extends or implements type Y, then X is a subtype of Y. See also supertype.

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super

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A Java keyword used to access members of a class inherited by the class in which it appears.

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superclass

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A class from which a particular class is derived, perhaps with one or more classes in between. See also subclass, subtype.

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supertype

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The supertypes of a type are all the interfaces and classes that are extended or implemented by that type. See also subtype, superclass.

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this

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A Java keyword that can be used to represent an instance of the class in which it appears. this can be used to access class variables and methods.

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throw

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A Java keyword that allows the user to throw an exception or any class that implements the "throwable" interface.

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throws

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A Java keyword used in method declarations that specify which exceptions are not handled within the method but rather passed to the next higher level of the program.

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try

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A Java keyword that defines a block of statements that may throw a Java language exception. If an exception is thrown, an optional catch block can handle specific exceptions thrown within the try block. Also, an optional finally block will be executed regardless of whether an exception is thrown or not.

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URN

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Uniform Resource Name. A unique identifier that identifies an entity, but doesn't tell where it is located. A system can use a URN to look up an entity locally before trying to find it on the Web. It also allows the Web location to change, while still allowing the entity to be found.

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wrapper

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An object that encapsulates and delegates to another object to alter its interface or behavior in some way.