Java by lanyuehua


									distingush between abstract and adopter class in java

when A class is An abstract means it declared with
keyword as public followed by asbtract. this makes
abstract class
can be only contain empty methods which are un
implemented.An abstract class cannot be instantiated.

Adapter is a special class that acts as an itermediary
between class and interface, therefore every interface
comes with an adapter with list of methods in it.

interface contains purely abstract class, this means
you can't define an interface mothods,therefore an
interface consist of methods which are off typed as
public and abstract only also as to a variables which
are off typed to as public static final types.

checked exception
during compiler process the compiler checks whether
exception has been handled or not such exceptions are
(IOExceptions error) since the program cant void such
unchecked exception
are those which compiler doesnt flag as potentially
error-prone during compiler runtime exceptions.

distingush between the following three types of
collections in java
List interface
the list interface specifies the mothods required to
process an ordered list of objects and such list may
contain repeatitions.
set interface
the set interafce defines the mothods required to
process a collection of objects in which there is no
repeatition and ordeing is unimportant.
Map interface
the map interface defines the methods required to
process a collection of objects consisting of pairs of
objects( keys and values)
Briefly describe how the generic mechanism of java
the generics mechanism allows us to send one or more
types to a class or inteface as a perameter

Describe each of the following ways of encoding data
text encoding
the text encoding means that the data are stored as a
charecter whereas on the other hand binary encoding,
means that the data is stored in the same format as
the internal representation used by the program to
store data in memory.

Describe what is mean by an enumerated type and
illustrate how the enumerated PlaneStatus type was
represented in UML.
enumerated is type that consist of a few possible
values each with meaningful name is refered to as an
enumerated type.

The Swing components support the ability to display
brief popup messages when the user rests the mouse
cursor over them. While the class used to display
popup messages is JToolTip, you never create instances
directly. Instead, you call the setToolTipText(String
text) JComponent, which triggers the text to be
displayed at the appropriate time.

immutable objects
is object which has no methods to alter their state
are know as immutable object.

is a java program that is downloaded and run from web
is each separate task performed by a single program.

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