Java Midterm Review
Chapter 2:
-Accessor method (getter method): A method that accesses an object and returns some
information and does not change internal data of object on which is invoked
-Mutator method: modifies the internal data of an object
-Java classes are grouped into packages
-Calling methods are used with a dot operator
-Void is used when a method has no return value
-Object reference: denote the memory location of an object
-Mainly about GUI’s
Chapter 3:
-Instance variables: store data of an object (private typeName variableName;)
-Instance of a class: an object of a class
-Encapsulation: process of hiding implementation details and providing methods for data access
-To encapsulate: declare variable as private and declare public methods to access the
variables
-implicit parameter: object on which the method is invoked
-Explicit parameter: all other parameter variables
-Local variable: variable that is declared in the body of a method
-Parameter variable: variables that are declared in method headers
Chapter 8:
Cohesive public interface: refers to a class should only represent a single concept and the
concept should be closely related to a single concept
Side effect of method: any kind of modification of data that is seen outside the method
-Mutator method’s side effect is the modification of implicit parameter
All caps usually means that you should use public static final
Static: shares memory, makes it the same property if new object is created
Java Packages: Set of related classes
Packaging classes is convenient to organizes classes but needs to avoid name clashes
Use the extend
Chapter 9
-Inheritance: relationship between a more general class (superclass) and a more specialized
class (called the subclass)
-substitution principle: you can always use a subclass object when a superclass object is
expected
-To implement subclass use the extends keyword
-Override: feature that allows a subclass to use the same name as the method from a superclass
-Overloading: when two methods have the same name but different parameter types
-Polymorphism: Allows you have one interface with multiple implementations(extends)
-Override toString(): Used to get a proper output when an object is used in print() or println()
-equals method: used to determine if 2 instances are equal
-instanceof Operator: used to test whether the object is an instance of the specified type (class
or subclass or interface)
Chapter 10
-Interface type: used to specify required operations
-Inner class: A class that is defined inside another class, can be declared inside an enclosing
class, but outside its methods
-Event Handling
objects
-Event listeners: indicates which events it needs to receive by installing event listener
-belongs in class provided by application programmer
-Methods describe the actions to be taken when an event occurs
Event source: User interface component that generates a particular event
-add an event listener object to the appropriate event source
-Button is created by using a JButton class, JButton button = new JButton (“Add Interest”);
-Javax.swing.Timer generates equally spaced timer events, sending events to installed action
listeners, useful when you want to have an object updated in regular intervals
-Mouse events listener is a component that is added by calling the addMouseListener method
-Call repaint is used to tell the component to repaint itself to show rectangle in new position
-When mouse is pressed, mouse listener moves rectangle to the mouse location
Chapter 11
-Scanner class used to read text files
-To read from disk file:
-File inputFile = new File(“input.txt”);
-Loop to process numbers in the input file:
While (in.hasNextDouble() ) {
Double value = in.nextDouble();
}
-To write a file, construct a PrintWriter object
PrintWriter out = new PrintWrite(“output.txt”);
-FileNotFoundException
-When the input or output file doesn’t exist, a FileNotFoundException can occur
-Text Input and Output
-next method of the scanner class reads a string that is delimited by white space
-delimiter(word separator): to print each word into separate lines, useDelimiter method
-White space include: spaces, tab characters, and the newline characters that separate lines
-Formatting output types: %d decimal integer, %f fixed floating-point, %e Exponential floatingpoint, %g General floating-point, %s String
-Command Line Arguments, is a method used to add extra information for the program to use
-useful for automating tasks
-program takes in command line arguments, an optional -d flag to indicate decryption
instead of encryption, input file name, and output file name
-Exception Handling – Throwing Exceptions
-Provides a flexible mechanism for passing control from the point of error detection to a
handler that can deal with error
-When exception is throw, method terminates immediately and the normal control flow is
terminated
-try statement contains one or more statements that may cause an exception to the kind that
you are willing to handle
-scanner constructor can throw a FileNotFoundException
-Scanner.next can throw a NoSuchElementException
-Integer.parseInt can throw a NumberFormatException
-Exceptions that you throw and catch can:
-Internal errors reported by the type Error
-RuntimeException
-check exceptions, indicates that something has gone wrong for external reasons
-out.close are used to close a resource