Introduction To Programming

Front 1

What does a class do?

Back 1

Describes all objects of a specific type.

Front 2

What is an object?

Back 2

Instances of a class.

Front 3

What are methods?

Back 3

Operations for an object (declared by the class).

Front 4

What are constructors?

Back 4

Methods that initialise an object when the object is first created, setting up any fields the object has.

Front 5

What does a user have to do to change the formal parameters of a method into actual parameters?

Back 5

When the method is invoked, the user has to input values for the formal parameters. These values, or actual parameters, are lost when the method finishes running.

Front 6

What are the three parts of a method header?

Back 6

Visibility modifier, return type and method name.

Front 7

What do fields define?

Back 7

The state of an object.

Front 8

What are the two main types of method?

Back 8

1. Mutator - "Set" method.

2. Accessor - "Get" method.

Front 9

What are local variables and where can they be accessed?

Back 9

They are variables initialised within a method & can only be accessed from within that method as they are only around when the method is running.

Front 10

What does changing the visibility modifier do?

Back 10

It changes whether or not other classes (and programmers) can see it (or call it).

Front 11

What is the structure of a conditional (if) statement?

Back 11

if(boolean condition) {

body

}

Front 12

What are the boolean operators?

Back 12

&& and

|| or

! not

Front 13

What is modularisation?

Back 13

Splitting a whole into well-defined parts (that can be built separately and interact in well-defined ways).

Front 14

What is abstraction?

Back 14

Ignoring details of parts to focus on a higher problem.

Front 15

What are 2 examples of primitive types?

Back 15

1. int

2. boolean

Front 16

What is an example (and a general rule) of object types?

Back 16

Example: String.

Rule: Any class can be an object type.

Front 17

What must you do for an object type that you don't need to do for a primitive one?

Back 17

Inside the constructor you must assign the field a new ClassName (actual parameters for this class).

Front 18

What does the modulo operator do?

Back 18

It gives the remainder after the division of integers.

Front 19

How do you call a method of an object type?

Back 19

fieldName.methodName([method'sactual parameters]);

Front 20

What is a generic class?

Back 20

A class that gets parameterised with a second type (like ArrayList).

Front 21

Does the size of an ArrayList have to be specified at initialisation?

Back 21

No, the size of an ArrayList is fluid, and will grow or shrink to accommodate deletion & creation of items.

Front 22

What are the four types of loop (in Java)?

Back 22

- For-each loop

- For loop

- While loop

- Do-while loop

Front 23

What is the syntax for a for-each loop?

Back 23

for(ElementTypeelement : collection) {

loopbody statements;

}

Front 24

What is the syntax for a while loop?

Back 24

while(boolean condition) {

loopbody statements;

}

Front 25

What is the syntax for a for loop?

Back 25

for(initialisation; condition; post-body action) {

loop body statements;

}

Initialisation& post-body action are usually to do with an int variable that is beingiterated a set number of times (as set out in the condition).

Front 26

What two methods does the Iterator class have to iterate over a collection?

Back 26

public boolean hasNext();

public ElementType next();

Front 27

When should you use an Array (over an ArrayList)?

Back 27

When you know the length of the collection of items.

Front 28

How are Arrays similar to ArrayLists?

Back 28

- You define them as a class field.

- You construct your array using the new keyword.

- When defining your array, you specify what type the objects/primitive values will be (this time in square brackets).

Front 29

What does 'Interface not Implementation' mean?

Back 29

You don't need to know how the program/class works - you just need to know that it does and how to use certain important parts of it.

Front 30

What is shown in documentation for a class?

Back 30

Anything with the visibility modifier of 'public'.

Front 31

What does API stand for?

Back 31

ApplicationProgramming Interface.

Front 32

What is different about a .equals() method vs using ==?

Back 32

The .equals() method tests for equality, while == tests for identity.

Front 33

What are HashMaps?

Back 33

Collections that contain pairs of values, each pair consisting of one key and one value.

Front 34

How do you initialise and then fill a HashMap?

Back 34

- To initialise it you create a field of type HashMap<type, type>; and then initialise it in the constructor using the new keyword.

- You use the .put(item, item); method to fill it.

Front 35

How do you lookup a value in a HashMap?

Back 35

You supply the key and the value is returned.

Front 36

What happens if you try to add the same pair into the HashMap?

Back 36

It does not add it, as HashMaps do not allow for duplicates.

Front 37

What is a HashSet?

Back 37

It is an ArrayList that does not allow for duplicates.

Front 38

How do you initialise and then fill a HashSet?

Back 38

- You initialise it as a field (written as HashSet<type>) and then use the new keyword to create it in the constructor.

- You fill it using the method .add(item);

Front 39

What does it mean to make a variable or method static?

Back 39

It means that variable/method does not belong to the object, it belongs to the class. They exist (and can be accessed) as soon as they are defined.

Front 40

What does it mean to make a variable final?

Back 40

It means once the variable has been assigned a value, that value cannot change.

Front 41

What happens to the written source code in order for it to be read and executed by the machine?

Back 41

It must be compiled into Java Virtual Machine Code, which is in turn interpreted by the VM interpreter that carries out the intended instructions in the code.

Front 42

What are 2 examples of compile-time errors?

Back 42

- Syntax errors (e.g. missing semicolon or curly bracket).

- Type errors (e.g. an int where a String was expected).

Front 43

What are the 2 types of run-time errors?

Back 43

- Given because your program does something illegal (e.g. NullPointerException).

- Not given but your program does not do what you want.

Front 44

What is encapsulation?

Back 44

It means to hide any unnecessary information from people using your code. It is useful when trying to prevent bugs.

Front 45

What two things help with the detection of bugs?

Back 45

Documentation and Modularisation.

Front 46

What does it mean to test a program?

Back 46

It means to search for the presence of errors. It is not easy to do well.

Front 47

What does debugging do?

Back 47

It searches for the source of errors, often far away from where the problem actually arose.

Front 48

What is unit testing?

Back 48

It means to test everything from single methods to entire packages. You should:

- Understand what the unit should do.

- Test boundary cases (e.g. full arrays, etc.).

- Look for violations (e.g. what happens if the input is negative?).

Front 49

What is the directory structure of a BlueJ project?

Back 49

- One bluej.pkg project file per project.

- One bluej.pkh backup file per project.

- One *.java source code file per class.

- One *.class byte code file per class.

- One *.ctxt context file per class.

Front 50

What does IDE stand for?

Back 50

Integrated Developing Environment.

Front 51

How do you compile at the command line?

Back 51

You type javac classname.java to compile the class ClassName and any classes dependent upon it.

Front 52

How do you execute at the command line?

Back 52

You type java ClassName followed by any arguments required by the main method to execute a class (as long as it has already been compiled).

Front 53

What is the header for a main method?

Back 53

publicstatic void main(String[] args)

Front 54

What is the difference between tight and loose coupling and which one do you want?

Back 54

Tight coupling is where one class relies heavily upon another, whereas loose coupling is where one class only passes parameters to another (and so they aren't dependant upon each other).

- You want loose coupling.

Front 55

What is the difference between high and low cohesion and which one do you want?

Back 55

- High cohesion - a unit is responsible for one single task.

- Low cohesion - a unit is responsible for many unrelated tasks.

- You want high cohesion.

Front 56

What is the difference between Responsibility-Driven Design (RDD) and Object-Oriented Design (OOD)?

Back 56

- Object-orienteddesign focuses on the client-server model, where both parties exchangeinformation based on a contract they both commit to.

- Responsibility-drivendesign on the other hand looks at the classes & says that the class thatstores the data should be responsible for manipulating it.

Front 57

What is refactoring?

Back 57

A class/method is looked at and restructured to eliminate redundancy and improvereadability.

Front 58

What are two types of recursive data structures?

Back 58

1. Simple list data structures

2. Tree data structures

Front 59

What do simple lists consist of?

Back 59

A HEAD (which is a list element) and a TAIL (which is a smaller list)

Front 60

What do trees consist of?

Back 60

A ROOT node and a number of SUB_TREEs (which are smaller trees).

Front 61

What are the two parts of a recursive definition?

Back 61

1. The base part.

2. The inductive part.