Array Lists Notes & HW
Array List study notes and homework at the bottom
Intro Notes
ArrayLists have a reference type The difference bewteeen Arrays and ArrayLists are that ArrayLists have a mutable size while Arrays do not. Can add, find size clear, remove at an index tet an index or checki if the list is empty for loop
Ehanced for loop "for each" iterates through each item in the ArrayList to directly get the token of the ArrayList
It's a way of organizing anything, particularly Java objects. ArrayLists can only store wrapper classes and java objects which differs from say lists or arrays.
Min Max
CAn iterate through and set a variable equal to comparison variable and continue until finished
Searching
a for loop looking for the index of a certain which can be done with a combination of if/else statements and other conditionals Order matters in a search, for instance if we have 5 ducks, it will iterate sequentially, sorts them in specified order, usually descending or ascending order through sort()
import java.util.ArrayList;
import java.util.Collections;
// Initializing an ArrayList filled with strings
ArrayList<String> strings = new ArrayList<>();
strings.add("5");
strings.add("5.0");
strings.add("5AB3");
strings.add("Eighty Six");
strings.add("86");
strings.add("Your mom");
strings.add("Cool");
// function to iterate and print out items
public void print(ArrayList<String> strings){
for (String str : strings){
System.out.println(str);
}
}
// 1st bullet (Sort an ArrayList in descending order and swap the first and last elements)
System.out.println("------------------");
Collections.sort(strings, Collections.reverseOrder());
System.out.println("Reverse Order: ");
print(strings);
System.out.println("Swap 1st & Last Element: ");
String temp = strings.get(0);
strings.remove(0);
strings.add(0,strings.get(strings.size()-1));
strings.remove(strings.size()-1);
strings.add(strings.size(), temp);
print(strings);
// Initializing an ArrayList filled with strings
ArrayList<String> strings = new ArrayList<>();
strings.add("5");
strings.add("5.0");
strings.add("5AB3");
strings.add("Eighty Six");
strings.add("86");
strings.add("Your mom");
strings.add("Cool");
// 2nd bullet point (Find and display the hashCode of an Arraylist before and after being sorted)
// hashCode before being sorted
System.out.println("Unsorted hashCode: " + strings.hashCode());
// sorted hashCode
Collections.sort(strings);
System.out.println("Sorted hashCode: " + strings.hashCode());