jshell> class GradeTracker {
   ...>     private ArrayList<Double> grades;
   ...>     private String studentName;
   ...>
   ...>     public GradeTracker(String name) {
   ...>         this.studentName = name;
   ...>         this.grades = new ArrayList<>();
   ...>     }
   ...>
   ...>     public void addGrade(double grade) {
   ...>         if (grade >= 0 && grade <= 100) {
   ...>             grades.add(grade);
   ...>             System.out.println("Added grade " + grade + " for " + studentName);
   ...>         } else {
   ...>             System.out.println("Invalid grade: " + grade + ". Must be 0-100.");
   ...>         }
   ...>     }
   ...>
   ...>     public void removeGrade(double grade) {
   ...>         if (grades.remove(grade)) {  // remove() returns true if found and removed
   ...>             System.out.println("Removed grade " + grade + " for " + studentName);
   ...>         } else {
   ...>             System.out.println("Grade " + grade + " not found for " + studentName);
   ...>         }
   ...>     }
   ...>
   ...>     public double getAverage() {
   ...>         if (grades.isEmpty()) {
   ...>             return 0.0;
   ...>         }
   ...>
   ...>         double sum = 0.0;
   ...>         for (double grade : grades) {
   ...>             sum += grade;
   ...>         }
   ...>         return sum / grades.size();
   ...>     }
   ...>
   ...>     public void printReport() {
   ...>         System.out.println("\n=== Grade Report for " + studentName + " ===");
   ...>         System.out.println("All grades: " + grades);
   ...>         System.out.println("Number of grades: " + grades.size());
   ...>         System.out.println("Average: " + String.format("%.2f", getAverage()));
   ...>
   ...>         if (!grades.isEmpty()) {
   ...>             double highest = grades.get(0);
   ...>             double lowest = grades.get(0);
   ...>
   ...>             for (double grade : grades) {
   ...>                 if (grade > highest) highest = grade;
   ...>                 if (grade < lowest) lowest = grade;
   ...>             }
   ...>
   ...>             System.out.println("Highest grade: " + highest);
   ...>             System.out.println("Lowest grade: " + lowest);
   ...>         }
   ...>         System.out.println("========================\n");
   ...>     }
   ...> }
|  created class GradeTracker

jshell> // Test the grade tracker
   ...> GradeTracker alice = new GradeTracker("Alice");
alice ==> GradeTracker@...

jshell> alice.addGrade(85.5);
Added grade 85.5 for Alice

jshell> alice.addGrade(92.0);
Added grade 92.0 for Alice

jshell> alice.addGrade(78.5);
Added grade 78.5 for Alice

jshell> alice.addGrade(88.0);
Added grade 88.0 for Alice

jshell> alice.printReport();

=== Grade Report for Alice ===
All grades: [85.5, 92.0, 78.5, 88.0]
Number of grades: 4
Average: 86.00
Highest grade: 92.0
Lowest grade: 78.5
========================

jshell> // Easy to add more grades - no size limit!
   ...> alice.addGrade(95.0);
Added grade 95.0 for Alice

jshell> alice.addGrade(82.5);
Added grade 82.5 for Alice

jshell> alice.printReport();

=== Grade Report for Alice ===
All grades: [85.5, 92.0, 78.5, 88.0, 95.0, 82.5]
Number of grades: 6
Average: 86.92
Highest grade: 95.0
Lowest grade: 78.5
========================

jshell> // Easy to remove a grade if there was an error
   ...> alice.removeGrade(78.5);
Removed grade 78.5 for Alice

jshell> alice.printReport();

=== Grade Report for Alice ===
All grades: [85.5, 92.0, 88.0, 95.0, 82.5]
Number of grades: 5
Average: 88.60
Highest grade: 95.0
Lowest grade: 82.5
========================

jshell> import java.util.Collections;

jshell> ArrayList<String> names = new ArrayList<>();
names ==> []

jshell> names.add("Charlie");
$21 ==> true

jshell> names.add("Alice");
$22 ==> true

jshell> names.add("Bob");
$23 ==> true

jshell> names.add("Diana");
$24 ==> true

jshell> System.out.println("Before sorting: " + names);
Before sorting: [Charlie, Alice, Bob, Diana]

jshell> // Sort alphabetically
   ...> Collections.sort(names);
jshell> System.out.println("After sorting: " + names);
After sorting: [Alice, Bob, Charlie, Diana]

jshell> // Shuffle randomly
   ...> Collections.shuffle(names);
jshell> System.out.println("After shuffling: " + names);
After shuffling: [Bob, Diana, Alice, Charlie]

jshell> // Sort numbers
   ...> ArrayList<Integer> numbers = new ArrayList<>();
numbers ==> []

jshell> numbers.add(45);
$25 ==> true

jshell> numbers.add(12);
$26 ==> true

jshell> numbers.add(78);
$27 ==> true

jshell> numbers.add(23);
$28 ==> true

jshell> System.out.println("Before sorting: " + numbers);
Before sorting: [45, 12, 78, 23]

jshell> Collections.sort(numbers);
jshell> System.out.println("After sorting: " + numbers);
After sorting: [12, 23, 45, 78]

jshell> // Creating and basic operations
   ...> ArrayList<String> list = new ArrayList<>();
list ==> []

jshell> list.add("item");           // Add to end
$31 ==> true

jshell> list.add(0, "first");       // Add at specific index
jshell> list.get(0);                // Get element at index
$32 ==> "first"

jshell> list.set(0, "new first");   // Replace element at index
$33 ==> "first"

jshell> list.remove("item");        // Remove by value
$34 ==> true

jshell> list.remove(0);             // Remove by index
$35 ==> "new first"

jshell> // Information methods
   ...> list.add("test");
$36 ==> true

jshell> list.size();                // Number of elements
$37 ==> 1

jshell> list.isEmpty();             // Check if empty
$38 ==> false

jshell> list.contains("test");      // Check if contains value
$39 ==> true

jshell> list.indexOf("test");       // Find index of value
$40 ==> 0

jshell> // Bulk operations
   ...> list.clear();               // Remove all elements
jshell> list.isEmpty();
$41 ==> true

jshell> class ShoppingList {
   ...>     private ArrayList<String> items;
   ...>
   ...>     public ShoppingList() {
   ...>         items = new ArrayList<>();
   ...>     }
   ...>
   ...>     public void addItem(String item) {
   ...>         if (!items.contains(item)) {
   ...>             items.add(item);
   ...>             System.out.println("Added: " + item);
   ...>         } else {
   ...>             System.out.println(item + " is already on the list");
   ...>         }
   ...>     }
   ...>
   ...>     public void removeItem(String item) {
   ...>         if (items.remove(item)) {
   ...>             System.out.println("Removed: " + item);
   ...>         } else {
   ...>             System.out.println(item + " was not on the list");
   ...>         }
   ...>     }
   ...>
   ...>     public void showList() {
   ...>         if (items.isEmpty()) {
   ...>             System.out.println("Shopping list is empty");
   ...>         } else {
   ...>             System.out.println("\nShopping List:");
   ...>             for (int i = 0; i < items.size(); i++) {
   ...>                 System.out.println((i + 1) + ". " + items.get(i));
   ...>             }
   ...>             System.out.println("Total items: " + items.size() + "\n");
   ...>         }
   ...>     }
   ...>
   ...>     public boolean hasItem(String item) {
   ...>         return items.contains(item);
   ...>     }
   ...> }
|  created class ShoppingList

jshell> // Test the shopping list
   ...> ShoppingList groceries = new ShoppingList();
groceries ==> ShoppingList@...

jshell> groceries.addItem("milk");
Added: milk

jshell> groceries.addItem("bread");
Added: bread

jshell> groceries.addItem("eggs");
Added: eggs

jshell> groceries.addItem("milk");  // Duplicate
milk is already on the list

jshell> groceries.showList();

Shopping List:
1. milk
2. bread
3. eggs
Total items: 3

jshell> groceries.removeItem("bread");
Removed: bread

jshell> groceries.showList();

Shopping List:
1. milk
2. eggs
Total items: 2

jshell> System.out.println("Need milk? " + groceries.hasItem("milk"));
Need milk? true