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CSE 2221 Final Exam/102 Q’s and A’s/100% Accurate
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CSE 2221 Final Exam/102 Q’s and A’s/100% Accurate
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CSE 2221 Final Exam/102 Q’s andA’s/100% Accurate
The Implements Relation - - The implements relation may hold between a
class and an interface. If C implements I then class C contains code for the
behavior specified in interface I. This means that C has method bodies for
instance methods whose contracts are specified in I.
The code of C looks like this:
class C implements I {
// bodies for methods specified in I
}
The implements relation allows you to separate contracts from their
implementations- a best practice for component design.
- The Extends Relation - - The extends relation may hold between: 2
interfaces or 2 classes.
If B extends A then B inherits all the methods of A. This means B implicitly
starts out with all the method contracts (for an interface) or all the method
bodies (for a class) that A has. B can then add more method contracts (for an
interface) or method bodies (for a class).
- Overloading - - A method (name) is overloaded when 2 or more methods
have the same name, in which case methods must differ in the number
and/or types of their formal parameters (which the compiler uses to
disambiguate them)
- Interface Extension - - If I1 and I2 are interfaces and I2 extends I1, then
the code of I2 looks like this:
interface I2 extends I1{
//contracts for methods added in I2
}
For interfaces all such methods are instance.
- Testing - - Testing is a technique for trying to refute the claim that a
method body is correct for the method contract. In other words, the goal of
testing is to show that the method body does not correctly implement the
contract i.e. that it is defective
- Tree Representation of Expression - - Each operand (1,2,3,4,5,..) of an
operator (+ - * /) must be evaluated before that operator can be evaluated
- Unit Testing - - Best practice to test individual units of components of
software (one class, one method at a time)
, - Integration Testing - - Testing what happens when multiple components
are put together into a larger system
- System testing - - testing a whole end-user system
- Method Correctness - - Look at method's contract, which is a specification
of its intended behaviors. The actual behaviors of the method (see body)
must be within the allowed behaviors of the method (see contract).
- Test Plan/Fixture - - A set of test cases for a given unit is called a test plan
or a test fixture for that unit
- Designing a test plan - - To make testing most likely to succeed in
revealing defects, best practices include: (1) Test boundary cases: smallest,
largest, and special values in the contract (2) test routine cases (3) test
challenging cases, ie ones that if you were writing the code, you might find
difficult or error prone
- Test cases - - Each input value and corresponding allowed/expected result
is a test case. Test cases that do not reveal a defect in the code do not help
us to refute a claim of correctness. Test cases exercises a single unit of code,
normally a method. Test cases should be small and independent of each
other.
- Replaces Mode - - Upon return from a method call, a replaces-mode
parameter has a value that might be changed from its incoming value, but
the method's behavior does not depend on its incoming value. A replaces-
mode parameter, e.g., x should not appear in the requires clause, and #x
should not appear in the ensures clause
- Declared/Static Type - - When a variable is declared using the name of an
interface as its type, e.g. NN k = new NN2(); then its declared/static type is
said to be an interface type (here declared type is NN). Best practice to
declare vars this way.
When a variable is declared using the name of a class as its type, e.g. NN2 k
= new NN2() then its declared type (or static type) is said to be a class
type.here declared type is NN2)
- Polymorphism - - Java decides which method body to use for any call to an
instance method based on the object type of the receiver. This type because
the class of the constructor is always a class type.
NN k = new NN2(); < NN2 is the object type of k
NN n = new NN2Override();
k.power(2); < uses method body for power from NN2
n.power(2);
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