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fcef123 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 | An example of a program that creates a list and stores five strings in it:
import java.util.ArrayList;
public class Example {
public static void main(String[] args) {
// ArrayList datatype
// each element: String datatype
// list name: names
// 'new' - initialise list object
ArrayList<String> names = new ArrayList<>();
names.add("Jack Java");
names.add("Paula Python");
names.add("Cinthia C");
names.add("Randy Rust");
names.add("Pia PHP");
System.out.println(names);
}
}
Program outputs:
[Jack Java, Paula Python, Cinthia C, Randy Rust, Pia PHP]
==============================================
List type
- List can store elements of various 'basic type'
- BUT type SPECIFICATION - CANT USE 'basic type'
- SPECIFICATION - need to use 'envelope class'
Basic type | Correspoding envelope class
int Integer
double Double
char Character
boolean Boolean
float Float
ArrayList<String> participants = new ArrayList<>();
participants.add("Ann Attendee");
ArrayList<Integer> results = new ArrayList<>();
results.add(3);
ArrayList<Character> chars = new ArrayList<>();
chars.add('x');
==============================================
list elements
add
ArrayList<String> attendees = new ArrayList<>();
attendees.add("Ann Attendee");
System.out.println(attendees); //[Ann Attendee]
attendees.add("Alex Attendee");
attendees.add("Winry Winner");
System.out.println(attendees); //[Ann Attendee, Alex Attendee, Winry Winner]
Program outputs:
[Ann Attendee]
[Ann Attendee, Alex Attendee, Winry Winner]
get
ArrayList<String> attendees = new ArrayList<>();
attendees.add("Ann Attendee");
attendees.add("Alex Attendee");
attendees.add("Winry Winner");
System.out.println(attendees.get(0)); //Ann Attendee
System.out.println(attendees.get(2)); //Winry Winner
// create new empty list
ArrayList<Integer> numbers = new ArrayList<>();
// from i=1 to 10, populate list with the 'multiple of 10'
for (int i=1; i<=10; i++) {
numbers.add(i * 10);
}
System.out.println(numbers);
System.out.println(numbers.get(0) + ", " + numbers.get(1));
System.out.println(numbers.get(9));
Program outputs:
Ann Attendee
Winry Winner
[10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
10, 20
100
add AT SPECIFIC IDX
remove
ArrayList<Double> results = new ArrayList<>();
results.add(1.0);
results.add(2.5);
results.add(8.5);
System.out.println(results); //[1.0, 2.5, 8.5]
results.add(0, 9.9); // add to start
System.out.println(results); //[9.9, 1.0, 2.5, 8.5]
results.add(1, 10.0); // add to index 1
System.out.println(results); //[9.9, 10.0, 1.0, 2.5, 8.5]
results.remove(0); // remove the first
System.out.println(results); //[10.0, 1.0, 2.5, 8.5]
results.remove(3); // remove from index 3
System.out.println(results); //[10.0, 1.0, 2.5]
Program outputs:
[1.0, 2.5, 8.5]
[9.9, 1.0, 2.5, 8.5]
[9.9, 10.0, 1.0, 2.5, 8.5]
[10.0, 1.0, 2.5, 8.5]
[10.0, 1.0, 2.5]
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