arrays
Refresher
Refresher
Refresher
int a = 9;
double d = 5.4;
char ch = 'x';
String str = "hello";
What do you do if you want to store many values?
You need one variable for each value
String colour01 = "red"
String colour02 = "blue"
String colour03 = "green"
String colour04 = "yellow"
String colour05 = "pink"
Can you use just one variable to hold many values?
How would you do it?
String colours = "red, blue, green, yellow, pink"
Issues?
- Long string
- How do you extract the values?
- Integers?
int
a
a =
1, 2, 3, 4, 5 ;
int
a
a =
1, 2, 3, 4, 5
{ };
int
a
a =
1, 2, 3, 4, 5
{ };
[]
int
a
a =
1, 2, 3, 4, 5
{ };
[]
String[] colours = {"red", "green", "blue", "yellow", "pink"};
char[] letters = {"a", "b"};
boolean[] a = {false, true, true, false, false};
float[] numbers = {3.14159};// VS Code Demonstration
int[] a = {1,2,3,4,5}
System.out.println(a[0]);
System.out.println(a[2]);
System.out.println(colours[3]);
{"red", 3, 3.45, 'c'}Problem solving
Problem solving
We want to schedule a weekly meetup for our group. To work out the best day to meet we started a poll asking the group members to choose one day of the week.
From the poll result, how do we work out the best day?
Problem solving
int mondayVote = ?;
int tuesdayVote = ?;
int wednesdayVote = ?;
int thursdayVote = ?;
int fridayVote = ?;
int saturdayVote = ?;
int sundayVote = ?;Without arrays, you would need 7 variables, one for each day in the week
string bestDay = "Monday";
int mostVotes = mondayVote;
if (tuesdayVote > mostVotes){
mostVotes = tuesdayVote;
bestDay = "Tuesday";
}
if (wednesdayVote > mostVotes){
mostVotes = wednesdayVote;
bestDay = "Wednesday";
}
if (thursday > mostVotes){
mostVotes = thursdayVote;
bestDay = "Thursday";
}
...
if (sundayVote > mostVotes){
mostVotes = sundayVote;
bestDay = "Sunday";
}Without arrays, you would need 7 variables, one for each day in the week
What if instead finding the best day in a given week, you have to find the best day in a given month?
What if instead finding the best day in a given week, you have to find the best day in a given month?
What if instead finding the best day in a given week, you have to find the best day in a given month?
What about the best day in a given year?
What about the best day in a given year?
i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}i
mostVotes
days[i]
mostVotes < days[i]
0
0
6
true
1
6
0
false
2
6
13
true
3
13
12
false
4
13
2
false
5
13
18
true
6
18
10
false
7
18
int[] days = {6, 0, 13, 12, 2, 18, 10};
int mostVotes = 0;
for (int i = 0; i < days.length; i++){
if (days[i] > mostVotes){
mostVotes = days[i];
}
}Minimal
By Daniel Sutantyo
Minimal
- 8
