Arraylists:
public class ArrayandArrayList {
public static void main(String[] args){
String[] fishArr = new String[4];
fishArr[0] = "trout";
fishArr[2] = "salmon";
fishArr[1] = "tuna";
fishArr[1] = "bass"; //overriding index 1
ArrayList<String> fishArrList = new ArrayList<>();
fishArrList.add("salmon");
fishArrList.add("trout");
fishArrList.add(1, "tuna");
fishArrList.set(1, "bass"); //overriding index 1
//fish.ArrayList.remove(1); remove index 1, everything slides down
String removedFish = fishArrList.remove(1); //setting the removed index equal to a new string; essentially storing the removed variable
String aFish = fishArrList.get(0); //setting a String at index 0 equal to a variable
for (int i = 0; i < fishArrList.size(); i++){
System.out.println(fishArrList.get(i));
}
System.out.println(fishArrList);
}
}
ArrayandArrayList.main(null)
salmon
trout
[salmon, trout]
public class ArrayandArrayList {
public static void main(String[] args){
ArrayList<Integer> myNumbers = new ArrayList<>();
myNumbers.add(4);
myNumbers.get(0);
}
}
ArrayandArrayList.main(null)
Traversing an ArrayList:
- Arrays in Java start at 0
- .length will return the number of indexes in an array
- traverse an array with a For Loop or a For-Each Loop
ArrayList<Integer> nums = new ArrayList<>(Arrays.asList(3, 1, 8));
for (int temp : nums) {
System.out.print(temp);
}
for (int i = 0; i < nums.size(); i++){
System.out.println(nums.get(i));
nums.remove(i);
i--;
}
System.out.println(nums);
3183
1
8
[]
public class ShoppingList {
private ArrayList<String> items;
public ShoppingList(ArrayList<String> newItemList) {
items = newItemList;
}
public ArrayList<String> removeAnItem(String itemToRemove) {
int count = 0;
ArrayList<String> removedItems = new ArrayList<String>();
for (int i = items.size() - 1; i >= 0; i--) {
if (items.get(i).equals(itemToRemove)) {
items.remove(i);
removedItems.add(itemToRemove);
count++;
}
}
return removedItems;
}
public static void main(String[] args){
ArrayList<String> newList = new ArrayList<>(Arrays.asList("Hello", "Hi"));
ShoppingList list = new ShoppingList(newList);
ArrayList<String> removed2Items = list.removeAnItem("Hello");
System.out.println(removed2Items);
}
}
ShoppingList.main(null)
[Hello]
Converting Array to Arraylist:
public class ArrayToArrayList {
public static void main(String[] args){
int[] Array = {3, 6, 1, 7, 3, 1};
ArrayList<Integer> aNewList = new ArrayList<>();
for (int temp : Array){
aNewList.add(temp);
}
System.out.println(aNewList);
}
}
ArrayToArrayList.main(null)
[3, 6, 1, 7, 3, 1]
import java.util.ArrayList;
import java.util.Arrays;
public class Assignment {
private String name;
private String course;
private int daysUntilDue;
private String description;
public Assignment(String name, String course, int daysUntilDue, String desc){
this.name = name;
this.course = course;
this.daysUntilDue = daysUntilDue;
description = desc;
}
public String getName(){
return name;
}
public String getCourse(){
return course;
}
public int getDaysUntilDue(){
return daysUntilDue;
}
public String getDescription(){
return description;
}
}
public class Agenda {
private ArrayList<Assignment> assignments;
public Agenda(){
assignments = new ArrayList<>();
}
public void addToAgenda(Assignment assignment){
int currentDaysUntilDue = assignment.getDaysUntilDue();
int indexToInsert = 0;
// Find the correct index to insert the assignment based on daysUntilDue
for (int i = 0; i < assignments.size(); i++){
Assignment currentAssignment = assignments.get(i);
if (currentDaysUntilDue < currentAssignment.getDaysUntilDue()){
indexToInsert = i;
break; // Found the correct index, exit the loop
}
}
// Insert the assignment at the correct index
assignments.add(indexToInsert, assignment);
}
public static void main(String[] args){
Assignment newAssignment = new Assignment("SampleName1", "APCS", 6, "");
Agenda newClass = new Agenda();
newClass.addToAgenda(newAssignment);
}
}
Agenda.main(null)