Collection Framework - Guided Exercise - InventoryManager – Mastering Java ArrayList

[akash-coded]

🧪 Exercise: InventoryManager – Mastering Java ArrayList

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📖 Context: Welcome to LambdaMart!

You’re now a junior backend engineer at LambdaMart, India’s fastest-growing AI-first online retail company.

Your first assignment? Build the Inventory Management Module using Java’s ArrayList collection.

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🧰 Objective

Master the following ArrayList operations:

• Adding, accessing, updating, removing elements

• Searching and filtering

• Sorting using Comparator

• Using .contains(), .indexOf(), .clear(), .isEmpty(), .size()

• Using Iterator, forEach, and Streams

• Ensuring clean code practices and naming conventions

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📦 Files to Create

• Product.java – Entity class

• InventoryManager.java – Business logic using ArrayList

• Main.java – Entry point and test

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🧩 Part 1: Define the Product class

Product.java

public class Product {
    private int id;
    private String name;
    private String category;
    private double price;
    private boolean inStock; // 🔄 dynamic stock tracking
// TODO: Constructor
// TODO: Getters and Setters
// TODO: toString method

}

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✅ Task A: Fill in the blanks

public Product(int id, String name, String category, double price, boolean inStock) {
    this.id = id;
    this.name = name;
    this.category = category;
    this.price = price;
    this.__________ = __________; // fill
}

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✅ Task B: Add the following methods:

• getId()

• getPrice()

• getCategory()

• setPrice(double newPrice)

• setInStock(boolean status)

Add Javadoc-style comments for each method.

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🧩 Part 2: Setup Inventory Manager

InventoryManager.java

import java.util.*;
public class InventoryManager {

private List<Product> inventory = new ArrayList<>();
public void addProduct(Product product) {
    // TODO: Add validation to avoid duplicate names
    inventory.add(product);
    System.out.println("✅ Product added: " + product);
}

public void displayAllProducts() {
    if (inventory.isEmpty()) {
        System.out.println("⚠️ Inventory is empty.");
        return;
    }

    for (Product p : inventory) {
        System.out.println(p);
    }
}

}

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✅ Task C: Fix the bug

List<Product> inventory;
inventory.add(new Product(1, "Phone", "Electronics", 29999, true));

🛠 Bug: NullPointerException
✍️ Write the fix:

// Fix: Initialize the list here

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🧩 Part 3: Modify Products

✅ Task D: Complete these methods

// Remove a product by ID
public void removeById(int id) {
    Iterator<Product> it = inventory.iterator();
    while (it.hasNext()) {
        Product p = it.next();
        if (__________) { // complete
            it.remove();
            System.out.println("🗑️ Removed product with ID: " + id);
            return;
        }
    }
    System.out.println("❌ Product ID not found.");
}

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// Update the price of a product
public void updatePrice(int id, double newPrice) {
    for (Product p : inventory) {
        if (p.getId() == id) {
            p.setPrice(newPrice);
            System.out.println("💸 Updated price for " + p.getName());
            return;
        }
    }
    System.out.println("❌ Product ID not found.");
}

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🧩 Part 4: Search & Filter

✅ Task E: Search by category

public void searchByCategory(String category) {
    for (Product p : inventory) {
        if (p.getCategory().equalsIgnoreCase(category)) {
            System.out.println("🔍 Found: " + p);
        }
    }
}

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✅ Task F: Filter by price range

public void filterByPrice(double min, double max) {
    inventory.stream()
             .filter(p -> p.getPrice() >= min && p.getPrice() <= max)
             .forEach(System.out::println);
}

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✅ Task G: Search by name fragment

public void searchByName(String nameFragment) {
    for (Product p : inventory) {
        if (p.getName().toLowerCase().contains(nameFragment.toLowerCase())) {
            System.out.println("🔎 Match: " + p);
        }
    }
}

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🧩 Part 5: Sorting Logic

✅ Task H: Sort products by price

public void sortByPriceAscending() {
    inventory.sort(Comparator.comparingDouble(Product::getPrice));
}

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✅ Task I: Sort by name alphabetically

public void sortByName() {
    inventory.sort(Comparator.comparing(p -> p.getName().toLowerCase()));
}

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🧩 Part 6: Utility Operations

✅ Task J: Utility Methods (complete signatures)

public int getTotalInventoryCount() {
    return inventory.________(); // fill
}
public void clearInventory() {

inventory.________(); // fill

System.out.println("🧹 Inventory cleared.");

}
public boolean isEmpty() {

return inventory.________(); // fill

}

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🧪 Part 7: Main Class for Testing

Main.java

🧩 Predict the output:

InventoryManager manager = new InventoryManager();
manager.addProduct(new Product(1, "Phone", "Electronics", 29999, true));

manager.addProduct(new Product(2, "Yoga Mat", "Fitness", 899, true));

manager.displayAllProducts();
manager.removeById(2);

manager.updatePrice(1, 27999);
manager.sortByPriceAscending();

manager.displayAllProducts();
manager.filterByPrice(500, 3000);

✍️ Predict:

• How many products remain?

• What's the price of product with ID 1?

• Which sort order will show first?

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🏁 Deliverables

Your submission must include:

• ✅ Fully working Product.java

• ✅ Completed InventoryManager.java with 10+ methods

• ✅ Working Main.java file demonstrating:

  • Product addition

  • Updates

  • Removal

  • Sorting

  • Searching

  • Filtering

• ✅ Console outputs for each operation

• ✅ A README-style summary of “What I learned about ArrayList”

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📘 Clean Code Tips Recap

Tip	Follow This
Use camelCase for methods and variables	getProductById, productList
Always check for null or empty lists	if (inventory.isEmpty())
Use meaningful method names	filterByPrice(), not method2()
Separate concerns	Keep model (Product) and logic (InventoryManager) apart
Don’t repeat yourself	Use contains(), avoid manual loops for searches

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🚀 Bonus Challenges

• Add a method to prevent duplicate product names

• Add stock quantity and auto-decrement on sale

• Add Map<Integer, Product> for fast ID lookup

• Add export to CSV functionality using FileWriter

• Add Set<Product> for unique inventory across warehouses

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[Sdey0907]

**

Task 1 - InventoryManager_Sayan Dey_Completed

**

InventoryManager.zip

[vbhavana1]

Bhavana

public class Product {
private int id;
private String name;
private String category;
private double price;
private boolean inStock;

public Product(int id, String name, String category, double price, boolean inStock) {
    this.id = id;
    this.name = name;
    this.category = category;
    this.price = price;
    this.inStock = inStock; 
}

public int getId() { return id; }

public double getPrice() { return price; }

public String getCategory() { return category; }

public String getName() { return name; }

public boolean isInStock() { return inStock; }

public void setPrice(double newPrice) { this.price = newPrice; }

public void setInStock(boolean status) { this.inStock = status; }

@Override
public String toString() {
    return String.format("Product{id=%d, name='%s', category='%s', price=%.2f, inStock=%b}",
                         id, name, category, price, inStock);
}

}
import java.util.*;

import java.util.stream.Collectors;

public class InventoryManager {
private List inventory = new ArrayList<>();
public void addProduct(Product product) {
if (inventory.stream().anyMatch(p -> p.getName().equalsIgnoreCase(product.getName()))) {
System.out.println(" Duplicate product name not allowed: " + product.getName());
return;
}
inventory.add(product);
System.out.println("Product added: " + product);
}

public void displayAllProducts() {
    if (inventory.isEmpty()) {
        System.out.println(" Inventory is empty.");
        return;
    }
    inventory.forEach(System.out::println);
}

public void removeById(int id) {
    Iterator<Product> it = inventory.iterator();
    while (it.hasNext()) {
        Product p = it.next();
        if (p.getId() == id) { 
            it.remove();
            System.out.println(" Removed product with ID: " + id);
            return;
        }
    }
    System.out.println(" Product ID not found.");
}

public void updatePrice(int id, double newPrice) {
    for (Product p : inventory) {
        if (p.getId() == id) {
            p.setPrice(newPrice);
            System.out.println("Updated price for " + p.getName());
            return;
        }
    }
    System.out.println(" Product ID not found.");
}

public void searchByCategory(String category) {
    inventory.stream()
             .filter(p -> p.getCategory().equalsIgnoreCase(category))
             .forEach(p -> System.out.println("Found: " + p));
}

public void filterByPrice(double min, double max) {
    inventory.stream()
             .filter(p -> p.getPrice() >= min && p.getPrice() <= max)
             .forEach(System.out::println);
}

public void searchByName(String nameFragment) {
    inventory.stream()
             .filter(p -> p.getName().toLowerCase().contains(nameFragment.toLowerCase()))
             .forEach(p -> System.out.println(" Match: " + p));
}

public void sortByPriceAscending() {
    inventory.sort(Comparator.comparingDouble(Product::getPrice));
}

public void sortByName() {
    inventory.sort(Comparator.comparing(p -> p.getName().toLowerCase()));
}

public int getTotalInventoryCount() {
    return inventory.size(); 
}

public void clearInventory() {
    inventory.clear(); 
    System.out.println("Inventory cleared.");
}

public boolean isEmpty() {
    return inventory.isEmpty(); 
}

}
public class Main {
public static void main(String[] args) {
InventoryManager manager = new InventoryManager();
manager.addProduct(new Product(1, "Phone", "Electronics", 29999, true));
manager.addProduct(new Product(2, "Yoga Mat", "Fitness", 899, true));

    manager.displayAllProducts();

    manager.removeById(2);
    manager.updatePrice(1, 27999);

    manager.sortByPriceAscending();
    manager.displayAllProducts();

    System.out.println("Filtered products (₹500 - ₹3000):");
    manager.filterByPrice(500, 3000);
}

}

[prasetha21-max]

package com.practice.problems.java;
import java.util.*;

public class LambdaMartInventory {
    public static void main(String[] args) {
        InventoryManager manager = new InventoryManager();
        
        manager.addProduct(new Product(1, "Phone", "Electronics", 29999, true));
        manager.addProduct(new Product(2, "Yoga Mat", "Fitness", 899, true));
        manager.displayAllProducts();

        manager.removeById(2);
        manager.updatePrice(1, 27999);

        manager.sortByPriceAscending();
        manager.displayAllProducts();

        manager.filterByPrice(500, 3000);
    }
}

class Product {
    private int id;
    private String name;
    private String category;
    private double price;
    private boolean inStock;

    public Product(int id, String name, String category, double price, boolean inStock) {
        this.id = id;
        this.name = name;
        this.category = category;
        this.price = price;
        this.inStock = inStock;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }

    public String getCategory() {
        return category;
    }

    public void setPrice(double newPrice) {
        this.price = newPrice;
    }

    public void setInStock(boolean status) {
        this.inStock = status;
    }

    public String toString() {
        return "Product[id=" + id + ", name=" + name + ", category=" + category +
               ", price=" + price + ", inStock=" + inStock + "]";
    }
}

class InventoryManager {
    private List<Product> inventory = new ArrayList<>();

    public void addProduct(Product product) {
        for (Product p : inventory) {
            if (p.getName().equalsIgnoreCase(product.getName())) {
                System.out.println("Duplicate product name not allowed: " + product.getName());
                return;
            }
        }
        inventory.add(product);
        System.out.println("Product added: " + product);
    }

    public void displayAllProducts() {
        if (inventory.isEmpty()) {
            System.out.println("Inventory is empty.");
            return;
        }
        for (Product p : inventory) {
            System.out.println(p);
        }
    }

    public void removeById(int id) {
        Iterator<Product> it = inventory.iterator();
        while (it.hasNext()) {
            Product p = it.next();
            if (p.getId() == id) {
                it.remove();
                System.out.println("Removed product with ID: " + id);
                return;
            }
        }
        System.out.println("Product ID not found.");
    }

    public void updatePrice(int id, double newPrice) {
        for (Product p : inventory) {
            if (p.getId() == id) {
                p.setPrice(newPrice);
                System.out.println("Updated price for " + p.getName());
                return;
            }
        }
        System.out.println("Product ID not found.");
    }

    public void searchByCategory(String category) {
        boolean found = false;
        for (Product p : inventory) {
            if (p.getCategory().equalsIgnoreCase(category)) {
                System.out.println("Found: " + p);
                found = true;
            }
        }
        if (!found) {
            System.out.println("No products found in category: " + category);
        }
    }

    public void filterByPrice(double min, double max) {
        boolean found = false;
        for (Product p : inventory) {
            if (p.getPrice() >= min && p.getPrice() <= max) {
                System.out.println(p);
                found = true;
            }
        }
        if (!found) {
            System.out.println("No products found in price range " + min + " - " + max);
        }
    }

    public void searchByName(String nameFragment) {
        boolean found = false;
        for (Product p : inventory) {
            if (p.getName().toLowerCase().contains(nameFragment.toLowerCase())) {
                System.out.println("Match: " + p);
                found = true;
            }
        }
        if (!found) {
            System.out.println("No product matches name fragment: " + nameFragment);
        }
    }

    public void sortByPriceAscending() {
        Collections.sort(inventory, new Comparator<Product>() {
            public int compare(Product p1, Product p2) {
                return Double.compare(p1.getPrice(), p2.getPrice());
            }
        });
    }

    public void sortByName() {
        Collections.sort(inventory, new Comparator<Product>() {
            public int compare(Product p1, Product p2) {
                return p1.getName().toLowerCase().compareTo(p2.getName().toLowerCase());
            }
        });
    }

    public int getTotalInventoryCount() {
        return inventory.size();
    }

    public void clearInventory() {
        inventory.clear();
        System.out.println("Inventory cleared.");
    }

    public boolean isEmpty() {
        return inventory.isEmpty();
    }
}