Chapter 6: Methods

Question 1

How should this expression (ternary operator) be read?

boolean-expression ? expression1 :expression2

Answer 1

Evaluate the boolean-expression. If it is true, then use expression1. Otherwise, use expression2.

Question 2

What is a method conceptually?

Answer 2

A collection of statements grouped together to perform an operation.

Question 3

What is a method that belongs to a class and not a specific instance called?

Answer 3

Static. The name of the class must be used in the scope of them.

Think Math.sqrt(…) and Math.sin(…)

Question 4

Why might we want to use methods?

Answer 4

Improve program readability.
Facilitate modular program development by breaking down programs into smaller, manageable pieces promoting incremental development practices.
Use stub methods to outline functionality before implementation (i.e., method definitions without statements written yet).
Avoid redundant code by centralizing logic in reusable methods.
Simplify program maintenance by requiring changes only in a single method.

Question 5

What are the advantages of modularity?

Answer 5

• Controlling complexity
• Maintain programmer sanity
• Readability
• Implementation details are hidden in the method
• Ease of debugging
• Easily disable parts of the program

Question 6

What is unit testing?

Answer 6

The process of individually testing a small part or unit of a program, typically a method.

Question 7

What are the parts of unit testing?

Answer 7

A testbench (a.k.a. test harness) is a separate program designed specifically to verify that a method produces the correct output for various input values. Each unique set of input values is called a test vector, and an effective test vector includes border cases.

Question 8

What are some additional considerations for test harnesses/testbenches?

Answer 8

A good test harness only displays messages when output values are incorrect. Manually examining a program’s output is both cumbersome and error-prone.

Question 9

How do you define a method?

Answer 9

With a method header within a class. The header specifies the modifiers, the return type (possibly void), the name of the method, and the method parameter list.

modifiers returnValue Type methodName (list parameters) {
method Body;
return; //terminates the method
}

Question 10

What are method parameters?

Answer 10

Parameters are assigned with argument values by position: First parameter with first argument, second with second, etc. A method definition may have multiple parameters, separated by commas.

Question 11

Can a method be defined with no parameters?

Answer 11

Yes, but a method definition with no parameters must still have the parentheses.

public static double printVolume( ) {
..
}

Question 12

How does a method return work?

Answer 12

It basically returns a value using a return statement.

Ex: return numToSquare * numToSquare; A method can only return one item. A return statement may appear as any statement in the method, not just the last. Multiple return statements may exist in a method. Control goes back to the calling program as soon as the first return statement is reached.

Question 13

How does the void return type work?

Answer 13

• If the return type is void, the return statement is optional.
• A return statement may appear as any statement in the method, not just the last.

Question 14

What is a method signature?

Answer 14

The method name and the parameters list together.

Question 15

What’s the program that calls the methods called?

Answer 15

Caller.

Question 16

What are the requirements for a method?

Answer 16

• The name of the method
• Argument (actual parameters to pass values) list. Could be a list of expressions or possibly empty.

Question 17

What are Hierarchical (Nested) Method Calls?

Answer 17

• A method’s statements may include method calls.
• For example: main() is a method, and it typically calls many other methods.

Question 18

What happens when a program calls a method?

Answer 18

Program control transfers to the called method, which runs and then returns control to the caller.

Question 19

When does a method return control to the caller?

Answer 19

When it reaches a return statement or the closing brace of the method.

Question 20

What is an activation record?

Answer 20

A memory record that stores a method’s parameters and variables, placed in the call stack.

Question 21

Where are activation records stored?

Answer 21

In a special memory area called the call stack (also known as execution stack, runtime stack, or machine stack).

Question 22

What happens when a method finishes executing in relation to the activation record and the call stack?

Answer 22

Its activation record is removed from the call stack.

Question 23

What order does the call stack follow?

Answer 23

Last-In, First-Out (LIFO)—the last method called is the first one to finish and be removed.

Question 24

What are the five steps when a method is invoked?

Answer 24

1. Memory is allocated for parameters and local variables.
2. Argument expressions are evaluated.
3. Argument values are assigned to parameters.
4. The method executes.
5. Upon return, parameter and local variable memory is released.

Question 25

What is a stack frame?

Answer 25

A memory block in the call stack that holds data for an active method call.

Question 26

What does a stack frame contain?

Answer 26

- Method parameters - Return address (where to go back after the method finishes) - Local variables

Question 27

What happens when a method returns in relation to the stack frame?

Answer 27

Its stack frame is discarded, and the program resumes from where it left off.

Question 28

What can a method's block of statements include?

Answer 28

- Branches (if-else statements) - Loops (for, while, do-while) - Assignments (variable updates) - Calls to other methods - Any other statements

Question 29

What is a good guideline for method size?

Answer 29

- A method should fit on one screen or window. - Ideally no more than ~30 lines of code. - This is a guideline, not a strict rule.

Question 30

What is pass-by-value in Java?

Answer 30

a value that is passed onto the a method from the main

Question 31

Where is the argument value stored in pass-by-value?

Answer 31

the arguments value is copied into local memory allocated for the parameter

Question 32

What happens if a method modifies a parameter passed by value?

Answer 32

Only the copy is changed. The original argument in the caller remains unchanged.

Question 33

What happens to a method’s local variables when it returns?

Answer 33

They are discarded and removed from memory.

Question 34

What is method overloading/method name overloading?

Answer 34

Methods with the same name but differing in the number or types of parameters.

Question 35

What's a cute fact about return values in method overloading?

Answer 35

* A method's return type does not influence overloading. * **Thus, having two same-named method definitions with the same parameter types but different return types will yield a compiler error.**

Question 36

True or false: The return type of the method is not part of the signature.

Answer 36

True. The return type of the method is not part of the signature. That is, overloaded methods cannot differ only by their return type.

Question 37

What is the scope of a variable?

Answer 37

The part of the program where the variable can be accessed or referenced.

Question 38

What is a local variable?

Answer 38

A variable declared inside a method. It can only be used within that method.

Question 39

How long does a local variable’s scope last?

Answer 39

From its declaration until the end of the block `{}` that contains it.

Question 40

When must a local variable be assigned a value?

Answer 40

Before it is used. Otherwise, the program won’t compile.

Question 41

What are method parameters, and what is their scope?

Answer 41

Method parameters are local variables whose scope lasts for the entire method.

Question 42

What is the scope of a loop variable?

Answer 42

From the opening brace `{` of the loop to the closing brace `}` of the loop.

Question 43

What is the scope of a method?

Answer 43

A method is accessible within the entire class from the class's opening `{` to its closing `}`.

Question 44

Can a method access another method in the same class?

Answer 44

Yes, regardless of the order the methods are defined.

Question 45

What does the public access modifier do?

Answer 45

It allows methods and fields to be accessed from other classes.

Question 46

What is method abstraction?

Answer 46

It means using a method without knowing its internal details (hiding implementation).

Question 47

Why is method abstraction important?

Answer 47

It simplifies programming by allowing developers to use methods without worrying about how they work internally.

Question 48

What is another name for method abstraction?

Answer 48

Information hiding or encapsulation.

Question 49

How does method abstraction benefit software development?

Answer 49

It keeps code modular, organized, and easier to maintain by hiding complex details.

Question 50

What happens if a method's implementation changes but its signature stays the same?

Answer 50

The client program will not be affected, since it only relies on the method's interface.

Question 51

What is stepwise refinement (divide-and-conquer)?

Answer 51

A technique where a program is broken into smaller subproblems to solve it piece by piece.

Question 52

How does stepwise refinement help in programming?

Answer 52

It makes complex problems easier to manage by solving small parts first and then combining the solutions.

Question 53

What is a perfect size array?

Answer 53

An array where the number of elements is exactly equal to the memory allocated.

Question 54

How is a perfect size array passed to a method?

Answer 54

Using only the array’s reference (no extra parameters needed).

Question 55

Can a method modify the original perfect size array when passed as a parameter?

Answer 55

Yes, because arrays are passed by reference, allowing direct modification.

Question 56

What is an oversize array?

Answer 56

An array where the number of elements used is less than or equal to the memory allocated (extra space may exist).

Question 57

How do you keep track of the used elements in an oversize array?

Answer 57

By using a separate integer variable that stores the current number of elements.

Question 58

How is an oversize array passed to a method?

Answer 58

By passing both the array reference and the current size as separate parameters.

Question 59

What happens if a method changes the size of an oversize array?

Answer 59

The new size must be returned by the method so the calling program knows the updated count.

Question 60

What does a method signature indicate about the expected array size?

Answer 60

A method signature can tell whether a perfect size or oversize array is expected as an argument.

Question 61

What is the method signature for a method that expects a perfect size array?

Answer 61

It has one parameter for the array reference but no parameter for the array size.

Question 62

What is the method signature for a method that expects an oversize array?

Answer 62

It has two parameters: one for the array reference and one for the array size.

Question 63

How does the return type help determine if a method uses a perfect size or oversize array?

Answer 63

If the method returns an array reference, it constructs a perfect size array. If it returns an int, it may use an oversize array, with the int indicating the new array size.

Question 64

What is the relationship between the method's return type and the array size used?

Answer 64

A method returning an array reference uses a perfect size array, while a method returning an int may use an oversize array, indicating the array's new size.

Question 65

Where are primitive type variables stored?

Answer 65

Primitive type variables are stored directly in the stack frame.

Question 66

How are primitive data types passed to a method?

Answer 66

Primitive data types are passed by value, meaning a separate copy of the variable value is passed to the method.

Question 67

What happens when an array is passed to a method?

Answer 67

The array's reference is copied to the method's stack frame.

Question 68

Where are array elements stored?

Answer 68

Array elements are stored on the heap, and only the reference to the array is stored in the stack frame.

Question 69

How is an array passed to a method?

Answer 69

An array is passed by reference, meaning both the calling and called methods have access to the array's elements, and any changes in the method affect the array.

Question 70

What is an error that unintentionally modifies data known as?

Answer 70

It is known as a side effect.

Question 71

What is a common error when working with arrays in methods?

Answer 71

A common error is trying to modify an array reference in a method.

Question 72

What happens when an array reference is passed to a method?

Answer 72

The reference itself is passed by value, meaning a method cannot change the argument's array reference since separate copies are stored in two different stack frames.

Question 73

Where are references to arrays stored?

Answer 73

References are stored in the stack frame, and while references can be swapped within a stack frame, the original references remain unchanged when the method returns.

Question 74

What does the fill() method do when passed an array reference?

Answer 74

It fills the array with a specified value. The reference to the array is passed by value, so the array contents are modified, but the reference itself cannot be changed.

Question 75

What is the purpose of a method that calculates a value based on an array without changing the array?

Answer 75

Such a method calculates and returns a value based on the array, without modifying the array contents.

Question 76

Fill in the blank: A method that changes an array's contents but not its size typically has a _______ return type.

Answer 76

void

Question 77

What is the purpose of a method that creates a new array or changes the array's size?

Answer 77

This method returns a new array reference since array references cannot be changed inside a method.

Question 78

What can be identified from a method signature when dealing with arrays?

Answer 78

The method's purpose can often be identified by its signature, whether it calculates a value, modifies the array's contents, or changes the array's size.

Question 79

True or False: A method can change the original array reference when passed as an argument.

Answer 79

False

Question 80

What happens to array references when a method is called?

Answer 80

Separate copies are stored in two different stack frames.

Question 81

What does the binarySearch() method do?

Answer 81

It returns the index of the target in the array or a negative number if the target is not found.

Question 82

What is an example of a method that modifies an array's contents?

Answer 82

void sort(int[] arrayReference)

Question 83

What is an example of a method that creates a copy of an array?

Answer 83

double[] copyOf(double[] arrayReference, int newLength)

Question 84

Fill in the blank: The contents of an array can be modified, but its _______ cannot be changed.

Answer 84

reference

Question 85

What type of return value does a method that calculates a value based on an array typically have?

Answer 85

It typically returns a value, not an array.