Basics

Question 1

How many characters can a long store?

long largest =

Answer 1

19 characters

Question 2

Can a comparison in Java have more than 2 sides? e.g.

while(!dice1 == dice2 ==dice3)

// all 3 dice match

?

Answer 2

No. Only 2 sides. So:

!(dice1 ==2 && dice2 == dice3)

while not
dice 1 is the same as dice 2
and
dice 2 is the same as dice 3

Question 3

Define a variable

Answer 3

a called message (with some rules) that has been stored under a variable name

Question 4

Variable Name rules?

Answer 4

1) starts with a lower case letter

2) must define the type (String, Boolean, Double, Int)

Question 5

Variable Name rules?

Answer 5

1) starts with a lower case letter

2) must define the type (String, Boolean, Double, Int, Char)

Question 6

Variable Name declaration rules?

Answer 6

1) starts with a lower case letter
2) must define the type (String, Boolean, Double, Int, Char)
3) camel case - mutiple words strung together, first word must be lower case followed by upper case on first letter of each subsequent word e.g. glasgowIsgreat = true;
4) cannot start with numbers
5) cannot start with ‘ or “
6) stick to standard text characters
7) make it mean something and simple (as long as you like)

String message = “Hello!”;

Question 7

double?

Answer 7

stores decimals, -ve numbers

1,1, 2.1345, -1.4e10

Question 8

char

Answer 8

stores individual characters

a, b, 1

Question 9

char

Answer 9

stores individual characters
(a, b, 1)
char d = ‘f’;

Not single ‘’

Question 10

boolean

Answer 10

stores T or F

boolean GlasgowIsgreat = true;

Question 11

What is camel case?

Answer 11

mutiple words strung together, first word must be lower case followed by upper case on first letter of each subsequent word e.g. glasgowIsgreat = true;

Question 12

What is the difference between doing maths using double and int?

Answer 12

Integer division - the remainders are left out!

int a = 3;
int b = 2;

a/b;
= 1 [not 1.5!]

Question 13

For integer division, how does Java get the remainder (how much is left)?

Answer 13

3 % 2 = 1
// can remove one 2 from 3, and we are left with 1

5 % 6 = 5
// all 5 are remaining

10 % 4 = 2

Question 14

What is the Order of Operations in Java?

Answer 14

1) not necessarily Left to Right
2) Order is:
*
/
+
-
* and / are done BEFORE + and -

3) If multiple / and *, they are done Left to Right

Question 15

When using brackets to specify the order of operations, which nested values are evaluated first?

Answer 15

the innermost
e.g.
(a(b + c))/(ac + b);

Question 16

If you want to divide two int variables and then do a standard double division i.e. change from int division to answer being a double?

e.g. double c = a/b

Answer 16

double c = 1.0*a/b;

1.0* converts a into a double and then the division is done as a double division

Question 17

What is casting?

Answer 17

Casting is converting one type to another and storing it in another variable
e.g.
convert d (a double variable) into an int and storing the result in c

Question 18

Can you cast from a double to a string?

Answer 18

NO

Question 19

What is a literal?

Answer 19

when we put actual values into the programme e.g.
String message = “Hola Chica!” –> is the literal

It is a hard coded value

Question 20

What is a method?

Answer 20

a function

Question 21

Can you put two variables inside the same scope, even if it's a different type? e.g.
int a = 5;
a = 6;
or
int a = 5;
int a = 6;

Answer 21

NEVER
int a = 5;
a = 6;

is correct

Question 22

Can you put two variables inside the same scope, even if it's a different type? e.g.
int a = 5;
a = 6;
or
int a = 5;
int a = 6;

Answer 22

NEVER
int a = 5;
a = 6;

is correct

Question 23

Can you put two variables inside the same scope, even if it's a different type? e.g.
int a = 5;
a = 6;
or
int a = 5;
int a = 6;

Answer 23

NEVER
int a = 5;
a = 6;

is correct

Question 24

How do you stop a programme from running from inside a programme?

What is the convention?

Answer 24

System.exit(int n);

Calling this method terminates your programme. The value n is passed back to whatever started your programme and the normal convention is:
N = 0 //sucessfully ran
N = 1 //unsuccessful

Question 25

What is overloading?

Answer 25

same name for two different methods but with different arguments e.g. to calculate the area of a rectangle ``` public static double rectangleArea (double width){ return rectangleArea(width, width); } ```

Question 26

What is the signature of a method?

Answer 26

its name and argument list computeArea(double myRadius)

Question 27

What are the 5 conditions in Java?

Answer 27

If Else Else if ==, not

Question 28

How do you write comments?

Answer 28

// ``` /* */ ```

Question 29

In conditions, what does == mean?

Answer 29

equals

Question 30

In conditions, what does != mean?

Answer 30

not equals

Question 31

>=

Answer 31

greater than or equal to

Question 32

<=

Answer 32

less than or equal to

Question 33

How do you string operations together?

Answer 33

&& (both conditions have to be true - and) || (either condition has to be true - or)

Question 34

When conducting string equality, how should we compare two strings?

Answer 34

if (a.equals(b)) {... } DO NOT DO: if(a==b){...}

Question 35

What questions can you ask yourself to develop a good testing mindset?

Answer 35

How can I convince myself that this programme works? What are good inputs to check (test cases)?

Question 36

The import command

Answer 36

imports a class e.g. Scanner import.util.Scanner;

Question 37

System.in

Answer 37

gets text entry from the user's keyboard

Question 38

System.in.read()

Answer 38

a method that calls the System.in

Question 39

nextLine()

Answer 39

collects all key presses and returns them into a String

Question 40

nextLine()

Answer 40

collects all key presses and returns them into a String

Question 41

What does \ denote?

Answer 41

A special character

Question 42

\t

Answer 42

tab

Question 43

\n

Answer 43

newline

Question 44

Java shortcuts: int i = 0; System.out.println(i); i++; What does i++ do?

Answer 44

increases i by 1 each time

Question 45

What are the 3 types of Loops java uses?

Answer 45

do Loops while Loops for Loops

Question 46

What is a loop?

Answer 46

a compound statement that keeps repeating until some condition is met. Scope rules apply!

Question 47

how do we start writing a do Loop?

Answer 47

``` do{ //some conditions } while(condition); ```

Question 48

if you declare a variable within it a loop, will it be visible outside the loop?

Answer 48

No But loops can see variables declared before the loop!

Question 49

how do we make a while loop?

Answer 49

``` while(condition){ //some condition } ```

Question 50

what is the difference between a do loop and a while loop?

Answer 50

do loop - checks the condition at the end while loop - checks the condition first

Question 51

What is a counter loop and can you give an example of a type of look that does this?

Answer 51

loops that change some variable at each iteration (e.g. i++) for loops

Question 52

What is a counter loop and can you give an example of a type of look that does this?

Answer 52

loops that change some variable at each iteration (e.g. i++) for loops

Question 53

What is the syntax for FOR loops?

Answer 53

for(, , ) variable : to use for the loop and its initialisation (can be declared here or earlier) e.g. i condition : has to be true for loop to keep looping change : how the variable should be changed at each iteration i++

Question 54

What does this mean? for(int i=0; i<=9; i++)

Answer 54

0, 1, 2, 3, 4, 5, 6, 7, 8, 9 | count up

Question 55

for(int i=9; i>=0; i--)

Answer 55

9, 8, 7, 6, 5, 4, 3, 2, 1, 0 | count down

Question 56

for(int i=0; i>=9; i+=4)

Answer 56

0, 4, 8

Question 57

int i=1;i<=20;i*=5

Answer 57

1, 5

Question 58

for(int i=0; i>=20; i*=5)

Answer 58

0000000 until programme ends

Question 59

for (;;) | ?

Answer 59

infinite loop

Question 60

What are the two loop commands?

Answer 60

break continue

Question 61

what is a break?

Answer 61

jumps out of the loop break;

Question 62

what is continue in a loop?

Answer 62

jumps straight to the next iteration (if there is one) e.g. prints only even numbers

Question 63

String.format?

Answer 63

a method that allows us to combine Strings and numbers with control over: - length - padding (with spaces) - number of digits after decimal point

Question 64

String line = String.format("%15s, %5d", name, age) What does %15s mean? What does %5d mean?

Answer 64

%15s string of 15 characters long. No truncation. %5d pads the integer to be total 5 characters

Question 65

%d

Answer 65

gets the integer as is

Question 66

%5d

Answer 66

pads the integer with spaces to give a length of at least 5

Question 67

%-5d

Answer 67

adds padding after the integer 23---

Question 68

%05d

Answer 68

pads with (0) instead of spaces 00023

Question 69

How do you string.format doubles?

Answer 69

%f e.g.%5.2f pads to at least 5 with 2 digits after the decimal point e.g. 3.1415 becomes -3.14 . counts as a character

Question 70

%7.2f

Answer 70

---3.14

Question 71

%7.3f

Answer 71

--3.142

Question 72

integers: | %05.2f

Answer 72

pads with 0 rather than space

Question 73

integers: | %-5.2f

Answer 73

does the padding after the number

Question 74

What does String[] args denote?

Answer 74

a placeholder for information we want to pass into our program.

Question 75

What does System.out.println() denote?

Answer 75

System is a built-in Java class that contains useful tools for our programs. out is short for “output”. println is short for “print line”.

Question 76

What does System.out.print(). denote?

Answer 76

this type of print statement outputs everything on the same line

Question 77

What does the {} denote

Answer 77

the scope of our classes and methods

Question 78

What does it mean when we say Java is a compiled programming language?

Answer 78

the code we write in a .java file is transformed into byte code by a compiler before it is executed by the Java Virtual Machine on your computer A compiler is a program that translates human-friendly programming languages into other programming languages that computers can execute. The compiling process catches mistakes before the computer runs our code.

Question 79

ava programs have at least one class and one main() method. What does the class mean? What does the main() mean?

Answer 79

Each class represents one real-world idea. The main() method runs the tasks of the program.

Question 80

What are the three primitive data types?

Answer 80

int double boolean

Question 81

What can char hold?

Answer 81

any character, like a letter, space, or punctuation mark must be surrounded by single quotes ''

Question 82

Is String an object?

Answer 82

YES

Question 83

How do we use a String literal? How do we call a String class to create a String object?

Answer 83

literal: A String literal is any sequence of characters enclosed in double-quotes (String greeting = "Hello World";) ``` class: create a new String object by calling the String class when declaring a String (String salutations = new String ("Hello World!"); ```

Question 84

What are the 3 escape sequences?

Answer 84

``` \" allows us to add " to a String value e.g. ("\"Hello World\"") // prints "Hello World" ``` ``` \\ allows you to print backlash \ ("This is the back slash symbol: \\") prints This is the back slash symbol:\ ``` ``` \n new line ("Hellow\nWorld!") prints: Hello World! ```

Question 85

What does static typicing mean?

Answer 85

Static typing helps because bugs are caught during programming rather than during execution of the code. Java programs will not compile if a variable is assigned a value of an incorrect type.