2221 Study Materials

Aliasing

A circumstance where two or more variables refer to the same object.

mutable type

A compound data type whose elements can be assigned new values.

immutable type

A data value which cannot be modified. Assignments to elements or slices (sub-parts) of immutable values cause a runtime error.

requires

A method precondition

postcondition

A statement of what must be true at the end of the execution of the code.

primitive type

A variable data type in which the variable's value is of the appropriate size and format for its type: a number, a character, or a boolean value.

Assume the precondition is true when the method is called.

According to the "contract" in design-by-contract, the implementer of a method is permitted to:

NaturalNumber

After execution of the following code, what is the declared type (static type) of nCopy? Natural Number n = new NaturalNumber1L(); Natural Number nCopy = new NaturalNumber2(n);

NaturalNumber2

After execution of the following code, what is the declared type (static type) of nCopy? Natural Number n = new NaturalNumber1L(); Natural Number nCopy = new NaturalNumber2(n);

B.)

Assume n is an int variable. Which Java expression is true exactly when n is an odd number, i.e., not divisible by 2, and should be used to check for this situation? A.) n % 2 == 1 B.) n % 2 != 0 C.) Both A and B D.) Neither A and B

A.

Consider the following method contract and client code: /** * Adds n to this. *@updates this *@ensures this = #this + n */ public void add(NaturalNumber n){...} ... NaturalNumber num = new NaturalNumber2(10); num.add(num); What is the value of num after the method call? A. Cannot tell from the information provided. B. num = 0 C. num = 10 D. num = 20

a formal parameter

Consider the following method signature: private static int examScore(int studentNumber) {} Here, studentNumber is called:

Interface

Description of the boundary between a system and everything else

Debugging

Finding and fixing problems in your algorithm or program.

Clears

For a method formal parameter, which parameter mode is the default when no parameter mode is specified in the method's contract?

extends

For two classes or interfaces, this relation causes B (given B extends A) to inherit all methods of A, but not the constructors

D.)

Given the following code and assuming that all necessary imports and the rest of the class are provided correctly, which of the statements below is true? SimpleWriter out = new SimpleWriter1L(); NaturalNumber n1 = new NaturalNumber1L(6); NaturalNumber n2 = new NaturalNumber1L(4); NaturalNumber n3 = new NaturalNumber1L(11); A.) The code will result in a run-time error. B.) The code will output "yes". C.) The code will output "no". D.) The code will not compile.

C.)

Given the following code and assuming that all necessary imports and the rest of the class are provided correctly, which of the statements below is true? SimpleWriter out = new SimpleWriter1l(); NaturalNumber n1 = new NaturalNumber1L(5); NaturalNumber n2 = n1; n2.decrement(); out.println("n2=" + n1 + ",n2 = " + n2); A.) The code will not compile. B.) The code will output "n1=5, n2=4". C.) The code will output "n1=4, n2=4". A.) The code will result in a run-time error.

The client code that calls the method

In design-by-contract, the code responsible for making sure the precondition (requires clause) is true when a method is called is:

none of these choices

In design-by-contract, when the precondition(requires clause) of a method is not satisfied the implementer of a method is obligated to:

B

In testing, which one of the following statements is true? A. Testing is capable of proving that a method body is correct B. Failing test cases allow testers to immediately figure out the source of the failure C. Test cases can indicate a method has problems, but not necessarily what they are D. Testing usually takes up only a small portion of software development time

Pass-by-value

Java uses what type of parameter passing?

aliases

Multiple variables that contain references to the same object.

Method Overriding

Providing a new implementation for an inherited method

method overriding

Providing a new implementation for an inherited method

Implements

Relation between a class and an interface in Java

clears

Resets to zero

Parameter Modes

Restores, Clears, Updates, Replaces

Testing

Showing that code is defective by executing it

implementer

Someone viewing a system from the inside

be legal in Java (though flagged by Checkstyle)

Suppose the method from question 1.2 is called in the following statement: int k = examScore(42); This call would certainly::

<img src="brutus.jpg" />

Suppose you want to display the image file brutus.jpg in a browser, along with other content as organized in the HTML file index.html. Both these files are in the same folder/directory. Which HTML code fragment in index.html will produce the desired result? (Note that a well-formed HTML document such as the one you were to create for project #1 is an XML document.)

oneToThree = 1.0 + 2.0 * r.nextDouble();

Suppose you want to set the double variable oneToThree to a random real number uniformly distributed in the interval [1.0, 3.0). You have made the following declaration: Random r = new Random1L(); noting that r.nextDouble() returns a random real number uniformly distributed in the interval [0.0, 1.0). Which statement will set oneToThree to the desired result?

method overloading

The ability to define two or more different methods with the same name but different method signatures.

B.

The interval-halving technique can be used to compute results for problems like guessing numbers and finding roots because: A. In Java, division by two throws away the remainder. B. The answer to the question you can ask to get information about the mid-point of the interval allows you to eliminate (as possible results) all points on one side of the mid-point. C. All numbers involved in the computation are non-negative. D. The function you are evaluating over the interval has no more than two maximum or minimum values in that interval.

Extends

The name of the inheritance relation in Java

Statement

The smallest element of a programming language which expresses an action to be carried out.

Object Type

The type of a variable used by Java to decide which method body to use in the presence of overriding

Reference type

Type of variable representing a memory address

D.

What are the values of array and str after the call to bar? private static void bar(String [] a, String s) { s = a[0] + "io"; a[0] = s; } ... String [] array = {"Oh"}; String str = "USA"; bar(array, str); A. array = {"Oh"}, str = "USA" B. array = {"Oh"}, str = "Ohio" C. array = {"Ohio"}, str = "Ohio" D. array = {"Ohio"}, str = "USA"

C.

What are the values of num1 and num2 after the call to foo? private static void foo (NaturalNumber n1, NaturalNumber n2) { n2 = n1.divide(n2); } ... NaturalNumber num1 = new NaturalNumber2(31); NaturalNumber num1 = new NaturalNumber2(4); foo(num1, num2); A. num1 = 31, num2 = 4 B. num1 = 31, num2 = 3 C. num1 = 7, num2 = 4 D. num1 = 7, num2 = 3

Unpredicted error

What happens if the client violates precondition of a method

A method appears multiple times within different classes related by inheritance, each time with the same argument types and number.

What is an overridden method?

Recursion

When a function calls itself.

A.)

Which statement is true when testing a method? A.) A single test case can show the presence of a defect in the method body. B.) Very thorough testing can prove the correctness of the method body. C.) Testing is generally considered an expensive waste of time in industry. D.) A single test case can show the absence of defects in the method body if it produces correct results for the particular choice of inputs in that test case.

C

With regards to testing best practices for unit testing methods, which of the following types of tests are not usually performed? A. Tests using easy or common values B. Tests that test the limits of possible values C. Tests with values that violate preconditions to check for error D. Tests that use values that might be difficult for the method under test

precondition

a condition that must be fulfilled before other things can happen or be done.

reference type

a data type that contains a pointer to the memory location of an object

array

a group of similar variables of the same type

ensures

a method postcondition

Design-by-contract

a particular approach that uses the documentation only to capture the design but also to encourage interaction among developers

formal parameter

a variable in a method definition; it is initialized with an actual parameter value when the method is called

restores

actions done to n must be undone so n is the same at start and finish

Expression

can be evaluated to produce a value

superclass/base class/parent class

class which has been extended by another class

replaces

does not use the original value of n (Copy From)

statement3

double x = rnd.nextDouble();

debugging

finding and repairing a defect in code

statement

if(x < 0.5){}

subinterface/derived interface/child interface

inherits all method declarations of the interface it inherits

information hiding

intentionally leaving out internal details of a system

Argument or Actual Parameter

provided when calling a method

implements

provides bodies for everything in the given interface

Abstraction

providing a valid cover story for the behavior of a system

expression3

ptsInInterval + 1;

expression

ptsInInterval < n

statement2

ptsInInterval = ptsInInterval + 1;

expression2

rnd.nextDouble();

client

someone viewing a system from the outside

updates

takes the original value of n and makes a new value

Polymorphism

the object reference is used to refer to objects with different forms

declared type

type of variable used by the java compiler to determine how the variable can be used

Declared type/Static type

variables are not defined before use

Object type/Dynamic type

variables must be defined before they are used

statement4

while(ptsInInterval < n){}

expression4

x < 0.5