Access to Class Methods

[ShadowWalker]

I have to deal with java much time so i am trying to remember some basic staff

I have one Big Class called Item and 4 other class (CPU , Mobo , Ram , Box) which extends the Item class then in my main program i create an ArrayList<ArrayList<Item>> and inside the ArrayList i have add 4 arraylist (ramList , moboList , cpuList , boxList) now i want to check for example if an object inside ramList is equals with an other object in ramList so i create a method in Ram class (which extends Item) which check if this object is equals with onother but I am trying to make a small example to see if it's works i have an error .. check my code below :

Item File

import java.util.Scanner;


public class Item {
	int productID;
	String companyName;
	String manufactureName;
	String date;
	String model;
	int cost;
	
	
	public int getPrice(){
		return cost;
	}
	
}

class CPU extends Item{
	
	int pins;
	int [] availablePins = {1150,1155,1556};
	Scanner input = new Scanner(System.in);
	
	public CPU(String model,int pins , int cost){
		this.cost = cost;
		this.model = model;
		boolean pinsChoose = false;
		
		while(!pinsChoose){
			for(int i = 0 ; i < availablePins.length ; i++){
				if(availablePins[i] == pins){
					pinsChoose = true;
				}
			}
			if(!pinsChoose){
				System.out.print("Wrong pins for the CPU.You can choose 1150 , 1555 , 1556 try again :");
				pins = input.nextInt();
			}
		}
		this.pins = pins;
	}

	void printInfo() {
		System.out.println(model + " " + pins );
	}


	boolean checkEquals(CPU other) {
		if(this.model.equalsIgnoreCase(other.model) && this.pins == other.pins){
			return true;
		}
		else{
			return false;
		}
	}


}

class Mobo extends Item{
	
	public Mobo(String model , int cost){
		this.model = model;
		this.cost = cost;
	}


	void printInfo() {
		System.out.println(model);
	}


	boolean checkEquals(Mobo object) {
		if(this.model.equalsIgnoreCase(object.model)){
			return true;
		}
		else{
			return false;
		}
	}

}

class Ram extends Item{
	String size ;
	Scanner input = new Scanner(System.in);
	String [] availableSize = {"2Gb","4GB"};
	String [] availableModel = {"DDR2" , "DDR3"};
	boolean wrongRamSize = true;
	boolean wrongModel = true;
	
	public Ram(String model , String size , int cost){
		this.cost = cost;
		while(wrongModel){
			for(int i = 0 ; i < availableModel.length ; i ++){
				if(availableModel[i].equalsIgnoreCase(model)){
					wrongModel = false;
				}
			}
			if(wrongModel){
				System.out.print("Wrong model of the Ram. Available models are DDR2 and DDR3 try again :");
				this.model = input.next();
			}
		}
		this.model = model;
		
		while(wrongRamSize){
			for(int i = 0 ; i < availableSize.length ; i ++){
				if(availableSize[i].equalsIgnoreCase(size)){
					wrongRamSize = false;
				}
			}
			if(wrongRamSize){
				System.out.print("Wrong size of the Ram. Available size are 2Gb and 4Gb try again :");
				this.size = input.next();
			}
		}
		this.size = size;
	}
	
	
	
	public void printInfo(){
		System.out.println(model + " "  + size);
	}

	
	boolean checkEquals(Ram other) {
		if(this.model.equalsIgnoreCase(other.model) && this.size.equals(other.size)){
			return true;
		}
		else{
			return false;
		}
	}


}

class Box extends Item{
	String [] availableModel = {"mini","med","max"};
	Boolean wrongModel = true;
	Scanner input = new Scanner(System.in);
	
	public Box(String model , int cost){
		this.cost = cost;
		while(wrongModel){
			for(int i = 0 ; i < availableModel.length ; i ++){
				if(availableModel[i].equalsIgnoreCase(model)){
					wrongModel = false;
				}
			}
			if(wrongModel){
				System.out.print("Wrong Size of the Box. Available Sizes are mini , med and max try again :");
				this.model = input.next();
			}
		}
		this.model = model;
	}


	void printInfo() {
		System.out.println(model);
	}

	
	boolean checkEquals(Box other) {
		if(this.model.equalsIgnoreCase(other.model)){
			return true;
		}
		else{
			return false;
		}
	}


}

and my main Class

public class WareHouse {
	ArrayList<Item> ramList = new ArrayList<>();
	ArrayList<Item> cpuList = new ArrayList<>();
	ArrayList<Item> boxList = new ArrayList<>();
	ArrayList<Item> moboList = new ArrayList<>();
	ArrayList<ArrayList<Item>> products = new ArrayList<>(); 
	OrderProducts orderManager ;
	SellProducts purchaseManager ;
	
	public WareHouse(){
		products.add(ramList);
		products.add(cpuList);
		products.add(moboList);
		products.add(boxList);
		
		Scanner inputReader = null;
		try{
			inputReader =new Scanner(new FileInputStream("C:\\users\\ShadowWalker\\Desktop\\stocks.txt")); 
		}catch(FileNotFoundException e){
			e.printStackTrace();
		}
		
		while(inputReader.hasNext()){
			String line = inputReader.nextLine();
			String [] tokens = line.split(" ");
			Item element ;
			if(tokens[0].equalsIgnoreCase("CPU")){
				element = new CPU(tokens[1],Integer.parseInt(tokens[2]), Integer.parseInt(tokens[3]));
				products.get(1).add(element);
			}else if(tokens[0].equalsIgnoreCase("Ram")){
				element = new Ram(tokens[1],tokens[2], Integer.parseInt(tokens[3]));
				products.get(0).add(element);
			}else if(tokens[0].equalsIgnoreCase("Mobo")){
				element = new Mobo(tokens[1],Integer.parseInt(tokens[2]));
				products.get(2).add(element);
			}else{
				element = new Box(tokens[1],Integer.parseInt(tokens[2]));
				products.get(3).add(element);
			}	
		}
		inputReader.close();
	}
	
	public static void main(String args[]){
		WareHouse element = new WareHouse();
		if(element.products.get(0).get(0).checkEquals( element.products.get(0).get(2))){
			System.out.println("yes");
		}
	}
}

in my main class i read a file which has all the products inside the warehouse and i put them in ramList , moboList , cpuList and boxList
and i making a small test to see if one object in ramList is equals with onother one inside the ram list.. but i get error because i didn't have the checkEquals in Item class ... but i don't understand why is that a problem.. cause element.products.get(0) is an ArrayList which holds Ram Objects ...

i can change line 46 with this one : if(((Ram) element.products.get(0).get(0)).checkEquals( (Ram) element.products.get(0).get(2))){
but i don't like this way.. i want to know why i have wrong with the code above..

[Junky]

When you get an error copy and paste the full and exact message here.

BTW, storing all your Lists in another List is not a good idea. It just makes the code hard to read and maintain.

[Tolls]

Also, the usual way of checking for equals is to override the base equals() method found in the Object class, not to write a brand new one.

[ShadowWalker]

thank you guys