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I have some problems with ArrayList (quiz of head first java)

I've just started learning java since last week. I'm using book called 'head first java' and i'm struggling with solving problems about ArrayList. Error says "The method setLocationCells(ArrayList) in the type DotCom is not applicable for the
arguments (int[])" and I haven't found the solution :( help me..!
enter image description here

This looks like a Locate & Conquer type game similar to the game named Battleship with the exception that this game is a single player game played with a single hidden ship in a single horizontal row of columnar characters. Rather simplistic but kind of fun to play I suppose. The hard part is to locate the hidden ship but once you've located it, conquering (sinking) it becomes relatively easy. I'm sure this isn't the games' intent since it is after all named "The Dot Com Game" but the analogy could be possibly helpful.
There are several issues with your code but there are two major ones that just can not be there for the game to work:
Issue #1: The call to the DotCom.setLocationCells() method:
The initial problem is located within the DotComGame class on code line 13 (as the Exception indicates) where the call is made to the DotCom.setLocationCells() method. As already mentioned in comments the wrong parameter type is passed to this method. You can not pass an int[] Array to the setLocationCell() method when this method contains a parameter signature that stipulates it requires an ArrayList object. The best solution in my opinion would be to satisfy the setLocationCells() method parameter requirement...supply an ArrayList to this method.
The reason I say this is because all methods within the DotCom class work with an established ArrayList and one of the tasks of one of these methods (the checkYourself() method) actually removes elements from the ArrayList which is easy to do from a collection but very cumbersome to do the same from an Array.
To fix this problem you will need to change the data type for the locations variable located within the DotComGame class. Instead of using:
int[] locations = {randomNum, randomNum + 1, randomNum + 2};
you should have:
ArrayList<Integer> locations = new ArrayList<>(
Arrays.asList(random, randomNum + 1, randomNum + 2));
or you could do it this way:
ArrayList<Integer> locations = new ArrayList<>();
locations.add(randomNum);
locations.add(randomNum + 1);
locations.add(randomNum + 2);
There are other ways but these will do for now. Now, when the call to the setLocationCells() method is made you ahouldn't get an exception this issue should now be resolved.
Issue #2: The call to the DotCom.checkYourself() method:
Again, this particular issue is located within the DotComGame class on code line 18 where the call is made to the DotCom.checkYourself() method. Yet another parameter data type mismatch. You are trying to pass a variable of type String (named guess) to this method whereas its signature stipulates that it requires an integer (int) value. That again is a no go.
To fix this problem you will need to convert the string numerical value held by the guess variable to an Integer (int) value. So instead of having this:
while(isAlive) {
String guess = helper.getUserInput("Enter a Number: ");
String result = theDotCom.checkYourself(guess);
// ... The rest of your while loop code ...
}
you should have something like:
while(isAlive) {
String guess = helper.getUserInput("Enter a Number: ");
/* Validate. Ensure guess holds a string representation
of a Integer numerical value. */
if (!guess.matches("\\d+")) {
System.err.println("Invalid Value (" + guess
+ ") Supplied! Try again...");
continue;
}
int guessNum = Integer.parseInt(guess);
String result = theDotCom.checkYourself(guessNum);
numOfGuesses++;
if (result.equals("kill")) {
isAlive = false;
System.out.println(numOfGuesses + " guesses!");
}
else if (result.equals("hit")) {
// Do Something If You Like
System.out.println("HIT!");
}
else {
System.out.println("Missed!");
}
}
Below is a game named Simple Battleship which I based off of your code images (please don't use images for code anymore - I hate using online OCR's ;)
BattleshipGame.java - The application start class:
import java.awt.Toolkit;
public class BattleshipGame {
public static int gameLineLength = 10;
public static void main(String[] args) {
GameHelper helper = new GameHelper();
Battleship theDotCom = new Battleship();
int score = 0; // For keeping an overall score
// Display About the game...
System.out.println("Simple Battleship Game");
System.out.println("======================");
System.out.println("In this game you will be displayed a line of dashes.");
System.out.println("Each dash has the potential to hide a section of a");
System.out.println("hidden Battleship. The size of this ship is randomly");
System.out.println("chosen by the game engine and can be from 1 to 5 sections");
System.out.println("(characters) in length. The score for each battle is based");
System.out.println("on the length of the game line that will be displayed to");
System.out.println("you (default is a minimum of 10 charaters). You now have");
System.out.println("the option to supply the game line length you want to play");
System.out.println("with. If you want to use the default then just hit ENTER:");
System.out.println();
// Get the desire game line length
String length = helper.getUserInput("Desired Game Line Length: --> ", "Integer", true, 10, 10000);
if (!length.isEmpty()) {
gameLineLength = Integer.parseInt(length);
}
System.out.println();
// Loop to allow for continuous play...
boolean alwaysReplay = true;
while (alwaysReplay) {
int numOfGuesses = 0;
/* Create a random ship size to hide within the line.
It could be a size from 1 to 5 characters in length. */
int shipSize = new java.util.Random().nextInt((5 - 1) + 1) + 1;
int randomNum = (int) (Math.random() * (gameLineLength - (shipSize - 1)));
int[] locations = new int[shipSize];
for (int i = 0; i < locations.length; i++) {
locations[i] = randomNum + i;
}
System.out.println("Destroy the " + shipSize + " character ship hidden in the");
System.out.println("displayed line below:");
System.out.println();
String gameLine = String.join("", java.util.Collections.nCopies(gameLineLength, "-"));
theDotCom.setLocationCells(locations);
// Play current round...
boolean isAlive = true;
while (isAlive == true) {
System.out.println(gameLine);
String guess = helper.getUserInput("Enter a number from 1 to " + gameLineLength
+ " (0 to quit): --> ", "Integer", 1, gameLineLength);
int idx = Integer.parseInt(guess);
if (idx == 0) {
System.out.println("Quiting with an overall score of: " + score + " ... Bye-Bye");
alwaysReplay = false;
break;
}
idx = idx - 1;
String result = theDotCom.checkYourself(idx);
numOfGuesses++;
System.out.println(result);
if (result.equalsIgnoreCase("kill")) {
Toolkit.getDefaultToolkit().beep();
isAlive = false;
/* Tally the score dependent upon the gameLineLength... */
if (gameLineLength <= 10) { score += 5; }
else if (gameLineLength > 10 && gameLineLength <= 20) { score += 10; }
else if (gameLineLength > 20 && gameLineLength <= 30) { score += 15; }
else if (gameLineLength > 30 && gameLineLength <= 40) { score += 20; }
else { score += 25; }
gameLine = gameLine.substring(0, idx) + "x" + gameLine.substring(idx + 1);
System.out.println(gameLine);
System.out.println(numOfGuesses + " guesses were made to sink the hidden ship.");
System.out.println("Your overall score is: " + (score < 0 ? 0 : score));
}
else if (result.equalsIgnoreCase("hit")) {
gameLine = gameLine.substring(0, idx) + "x" + gameLine.substring(idx + 1);
}
if (result.equalsIgnoreCase("miss")) {
score -= 1;
}
System.out.println();
}
// Play Again? [but only if 'alwaysReplay' holds true]
if (alwaysReplay) {
String res = helper.getAnything("<< Press ENTER to play again >>\n"
+ "<< or enter 'q' to quit >>");
if (res.equalsIgnoreCase("q")) {
System.out.println("Quiting with an overall score of: " + score + " ... Bye-Bye");
break;
}
System.out.println();
}
}
}
}
GameHelper.java - The GameHelper class:
import java.util.Scanner;
public class GameHelper {
private final Scanner in = new Scanner(System.in);
public String getUserInput(String prompt, String responseType, int... minMAX) {
int min = 0, max = 0;
if (minMAX.length == 2) {
min = minMAX[0];
max = minMAX[1];
}
if (minMAX.length > 0 && min < 1 || max < 1) {
throw new IllegalArgumentException("\n\ngetUserInput() Method Error! "
+ "The optional parameters 'min' and or 'max' can not be 0!\n\n");
}
String response = "";
while (response.isEmpty()) {
if (prompt.trim().endsWith("-->")) {
System.out.print(prompt);
}
else {
System.out.println(prompt);
}
response = in.nextLine().trim();
if (responseType.matches("(?i)\\b(int|integer|float|double)\\b")) {
if (!response.matches("-?\\d+(\\.\\d+)?") ||
(responseType.toLowerCase().startsWith("int") && response.contains("."))) {
System.err.println("Invalid Entry (" + response + ")! Try again...");
response = "";
continue;
}
}
// Check entry range value if the entry is to be an Integer
if (responseType.toLowerCase().startsWith("int")) {
int i = Integer.parseInt(response);
if (i != 0 && (i < min || i > max)) {
System.err.println("Invalid Entry (" + response + ")! Try again...");
response = "";
}
}
}
return response;
}
public String getUserInput(String prompt, String responseType, boolean allowNothing, int... minMAX) {
int min = 0, max = 0;
if (minMAX.length == 2) {
min = minMAX[0];
max = minMAX[1];
}
if (minMAX.length > 0 && min < 1 || max < 1) {
throw new IllegalArgumentException("\n\ngetUserInput() Method Error! "
+ "The optional parameters 'min' and or 'max' can not be 0!\n\n");
}
String response = "";
while (response.isEmpty()) {
if (prompt.trim().endsWith("-->")) {
System.out.print(prompt);
}
else {
System.out.println(prompt);
}
response = in.nextLine().trim();
if (response.isEmpty() && allowNothing) {
return "";
}
if (responseType.matches("(?i)\\b(int|integer|float|double)\\b")) {
if (!response.matches("-?\\d+(\\.\\d+)?") ||
(responseType.toLowerCase().startsWith("int") && response.contains("."))) {
System.err.println("Invalid Entry (" + response + ")! Try again...");
response = "";
continue;
}
}
// Check entry range value if the entry is to be an Integer
if (responseType.toLowerCase().startsWith("int")) {
int i = Integer.parseInt(response);
if (i != 0 && (i < min || i > max)) {
System.err.println("Invalid Entry (" + response + ")! Try again...");
response = "";
}
}
}
return response;
}
public String getAnything(String prompt) {
if (prompt.trim().endsWith("-->")) {
System.out.print(prompt);
}
else {
System.out.println(prompt);
}
return in.nextLine().trim();
}
}
Battleship.java - The Battleship class:
import java.util.ArrayList;
public class Battleship {
private ArrayList<Integer> locationCells;
public void setLocationCells(java.util.ArrayList<Integer> loc) {
locationCells = loc;
}
// Overload Method (Java8+)
public void setLocationCells(int[] loc) {
locationCells = java.util.stream.IntStream.of(loc)
.boxed()
.collect(java.util.stream.Collectors
.toCollection(java.util.ArrayList::new));
}
/*
// Overload Method (Before Java8)
public void setLocationCells(int[] loc) {
// Clear the ArrayList in case it was previously loaded.
locationCells.clear();
// Fill the ArrayList with integer elements from the loc int[] Array
for (int i = 0; i < loc.length; i++) {
locationCells.add(loc[i]);
}
}
*/
/**
* Completely removes one supplied Integer value from all elements
* within the supplied Integer Array if it exist.<br><br>
*
* <b>Example Usage:</b><pre>
*
* {#code int[] a = {103, 104, 100, 10023, 10, 140, 2065};
* a = removeFromArray(a, 104);
* System.out.println(Arrays.toString(a);
*
* // Output will be: [103, 100, 10023, 10, 140, 2065]}</pre>
*
* #param srcArray (Integer Array) The Integer Array to remove elemental
* Integers from.<br>
*
* #param intToDelete (int) The Integer to remove from elements within the
* supplied Integer Array.<br>
*
* #return A Integer Array with the desired elemental Integers removed.
*/
public static int[] removeFromArray(int[] srcArray, int intToDelete) {
int[] arr = {};
int cnt = 0;
boolean deleteIt = false;
for (int i = 0; i < srcArray.length; i++) {
if (srcArray[i] != intToDelete) {
arr[cnt] = srcArray[i];
cnt++;
}
}
return arr;
}
public String checkYourself(int userInput) {
String result = "MISS";
int index = locationCells.indexOf(userInput);
if (index >= 0) {
locationCells.remove(index);
if (locationCells.isEmpty()) {
result = "KILL";
}
else {
result = "HIT";
}
}
return result;
}
}

How can I stop a method updating an array outside of it

Hoping for some help - I've been asked to write a hotel room system using methods for uni. All has been going well until I try to order the array alphabetically.
I have managed to get it to order within the method but it updated the main array (hotel). I want it to keep it within the order method, if that makes sense?
I've included a cut down version below without all the functions.
Currently it will reorder the array hotel so if you view the rooms the array will print like 'e,e,e,etc, George, Peter, Robert' instead of keeping its original form 'e, Robert, Peter, e,e,etc, George'
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String roomName;
int roomNum = 0;
String[] hotelRef = new String[12];
String[] hotel = new String[12];
initialise(hotel); //initialise
while (roomNum < 13) {
System.out.println("Please select from the menu:");
System.out.println("V : View rooms");
System.out.println("O : Order Guests alphabetically");
String selection = input.next();
switch (selection) {
//There are more switch cases on the original version
case "O":
order(hotel);
break;
default:
System.out.println("");
}
}
}
private static void order(String[] hotelRef) {
int j;
boolean flag = true; //will determine when the sort is finished
String temp;
String[] order = new String[12];
order = hotelRef;
while (flag) {
flag = false;
for (j = 0; j < order.length - 1; j++) {
if (order[j].compareToIgnoreCase(order[j + 1]) > 0) {
//ascending sort
temp = order[j];
order[j] = order[j + 1]; // swapping
order[j + 1] = temp;
flag = true;
}
}
}
for (int y = 0; y < order.length; y++) {
if (!order[y].equals("e")) {
System.out.println("Room " + y + " is occupied by " + order[y]);
}
}
System.out.println("Ordering completed");
}

You should clone the hotelRef instead of assigning the reference like this order = hotelRef;
You could do the following while creating the order array :
String[] order = new String[hotelRef.length]; // to make sure that order has the right size.
and instead of order = hotelRef;
for (int i=0;i<order.length;i++)
order[i]=hotelRef[i]; // thereby cloning
or use System.arraycopy() or any other method to accomplish cloning the array.

You can make copy of hotel array in your order method:
String[] hotelCopy = new String[hotelRef.length];
System.arraycopy(hotelRef, 0, hotelCopy, 0, hotelRef.length);
And then just use hotelCopy inside your order method.

The problem lies with the following line
order = hotelRef;
Change it to
order = hotelRef.clone();
Though you are creating a new object, you have assigned the reference to outer object only. So whatever changes you make in the inner object it will be reflected to the outer object.

Sorting array list

public class Saleitem {
public Product product = null;
public int numberofproduct = 0;
static ArrayList<Saleitem> Saleitemarray = new ArrayList<Saleitem>();
static ArrayList<Integer[]> total = new ArrayList<Integer[]>();
//read the sales data
public static void salesData() {
String SalesDataCSV = "SalesData.csv";
BufferedReader br = null;
String line = "";
String cvsSplitBy = ",";
System.out.println("\nThe Sales Data file has been opened\n");
try {
int currentcustomer = 1;
int lastcustomer = 1;
double sum = 0;
br = new BufferedReader(new FileReader(SalesDataCSV));
line = br.readLine();
System.out.println("-----------------------------------------------");
System.out.println("Sales Data File");
System.out.println("Customer ID, Product ID, Number of Units");
System.out.println("-----------------------------------------------");
while ((line = br.readLine()) != null) {
String field[] = line.split(cvsSplitBy);
if(field.length>1) {
String currentcustomerID = field[0];
String currentproductID = field[1];
String currentunitnumber = field[2];
Product currentproduct = null;
currentcustomer = Integer.parseInt(currentcustomerID);
int currentproductid = Integer.parseInt(currentproductID);
int currentproductunit = Integer.parseInt(currentunitnumber);
//-------------------------------------
// START OF PRODUCT/SALE ITEM PROCESSING
//-------------------------------------
System.out.println(currentcustomer + " , " + currentproductid + " , " + currentproductunit);
////////////////////
if (lastcustomer == currentcustomer) {
Saleitem salesItemObject = new Saleitem(currentproductid, currentproductunit,
Product.getUnitPrice(currentproductid));
Saleitemarray.add(salesItemObject);
} else {
// sale receipt date, time, etc.
Salereceipt salesReceiptObject = new Salereceipt(lastcustomer, lastcustomer,
sum, "2/20/16", (int) (Math.random() * 2000));
Salereceipt.receipt.add(salesReceiptObject);
lastcustomer = currentcustomer;
Saleitemarray.clear();
sum = 0;
}
///////////////////////////
//Find the correct product that the customer ordered
for (int i = 0; i < Product.productData.size(); i++){
if (((Product.productData).get(i)).productID == currentproductid){
currentproduct = Product.productData.get(i);
}
}
Saleitem salesItemObject = new Saleitem(currentproduct, currentproductunit);
Saleitemarray.add(salesItemObject);
boolean found = false;
//update total
for (int i = 0; i < total.size(); i++){
//total is an array of arrays =)
//in the array, index 0 is the productID
// index 1 is the total sold of that product
//Find the correct product total
if ((total.get(i))[0] == salesItemObject.product.productID){
//if we found it then we will mark found
//so that we can add in the item if it doesnt exist
//in our total array
found = true;
//increment the total number of prodcuts sold
(total.get(i))[1] += salesItemObject.numberofproduct;
}
}
if (found == false){
Integer[] array = new Integer[2];
// index 0 = product id
// index 1 = total number of products sold
array[0] = salesItemObject.product.productID;
array[1] = salesItemObject.numberofproduct;
total.add(array);
}
//-------------------------------------
// END OF PRODUCT/SALE ITEM PROCESSING
//-------------------------------------
//this is done inside of the constructor
if (currentcustomer == lastcustomer){
sum += currentproduct.productPrice * currentproductunit;
}
}
}
The Sales Data is imported from a file that has Customer_ID[0], Product_ID[1], Units_ordered[2]
I want to sort the ArrayList total by the Product_ID in ascending order. What would be the best way to do this. Im new to java so I don't know much of the syntax.

total.sort((item1, item2) -> item1.getProductId() - item2.getProductId());

You can use Collections#sort like below.
Add a getter for ProductId and you're done
Collections.sort(total, new Comparator<Saleitem>(){
#Override
public int compare(Saleitem s1, Saleitem s2) {
return s1.getProductId() - s2.getProductId();
}
});

ArrayList vs. Array. Why is one working and one isn't?

I've been trying to switch an older assignment over from an array to an arraylist, but for whatever reason my find method is not working when I modify it to use arrayList.. Seems to always be returning -1.
This is part of a large class so I don't want to include everything unless completely necessary, but I did include the declarations in case they are important:
public class Switch {
private SwitchEntry[] camTable;
private int numEntries;
private int maxEntries;
public Switch() {
camTable = new SwitchEntry[100]; // default value
numEntries = 0;
maxEntries = 100;
}
public Switch(int maxEntries) {
camTable = new SwitchEntry[maxEntries];
numEntries = 0;
this.maxEntries = maxEntries;
}
Original:
public int find (MACAddress source) {
int found = -1;
for (int i=0; i < numEntries; i++)
if (source.isEqual (camTable[i].getAddress())){
found = i;
break;
}
return found;
}
Modified:
public int find (MACAddress source) {
int found = -1;
for (int i=0; i < numEntries; i++)
if (source.isEqual (camTable.get(i).getAddress())){
found = i;
break;
}
return found;
}
Where numEntries is modified & where the new entries are added into the arrayList:
public void processFrame(Frame inFrame) {
// first, add source MAC to camTable if not already there
if (find(inFrame.getSource()) == -1) {
if (numEntries >= maxEntries) {
System.out.println ("Error...camTable is full - cannot add " + inFrame.getSource());
} else {
camTable.add(new SwitchEntry(inFrame.getSource(), inFrame.getPort())); //PROBLEM LINE
System.out.println ("Adding " + inFrame.getSource() + " to camTable");
}
}
//process frame
int index = find(inFrame.getDestination());
if (index != -1){
System.out.print ("Sending frame with data " + inFrame.getData() + " from " + inFrame.getSource() + " to " + inFrame.getDestination());
System.out.println (" out port " + camTable.get(index).getPort() );
} else {
System.out.print ("Flooding frame with data " + inFrame.getData() + " from " + inFrame.getSource() + " to " + inFrame.getDestination());
System.out.println (" out all ports" );
}
}
Solution:
camTable.add(numEntries++, new SwitchEntry(inFrame.getSource(),inFrame.getPort()));

Try This
public int find (MACAddress source) {
int found = -1;
ArrayList<MACAddress> camTable = new ArrayList<MACAddress>();
ListIterator<MACAddress> itr = camTable.listIterator();
while(itr.hasNext()){
MACAddress tempAdd = itr.next();
if(source.getAddress().equals(tempAdd.getAddress())){
found = itr.nextIndex();
return found;
}
return found;
}
I assume in ArrayList you store the objects of MACAddress. in if condition i check the source.getAddress to tempAdd.getAddress() is same then it will retun index of ArrayList. here ArrayList is local variable but you can create as a class variable

Use Contain method of collection.(ArrayList)
http://www.tutorialspoint.com/java/util/arraylist_contains.htm

Solution was straight-forward and just an oversight by me. All I had to do was add numEntries back into my add statement, which I neglected to fix after changing from an array to arrayList
Solution is posted in the original question now:

Temp arrays not working after adding 3rd Item

I had to make a Temp array to keep resizing the array list if the user decides to keep adding items to the cart, but my Temp array works until I try to add 3 different items to the cart.
I was instructed to do it this way instead of an array list to show the difficulty of arrays.
orderProduct [productCount] = aProduct;
orderQuantity [productCount] = aQuantity;
}
}

You forgot to increase productCount when there is already a product in the cart.
Moreover, you can just set the product and quantity array to the temp arrays instead of copying back.
orderProduct = tempOrderedProducts;
orderQuantity = tempOrderedQuantity;

Because you forgot productCount++ after resizing the array.
The following code will work:
public void setOrderProduct(Product aProduct, int aQuantity) {
if (productCount == 0) {
orderProduct[0] = aProduct;
orderQuantity[0] = aQuantity;
} else {
Product[] tempOrderedProducts = new Product[orderProduct.length + 1];
int[] tempOrderedQuantity = new int[orderQuantity.length + 1];
for (int i = 0; i < orderProduct.length; i++) {
tempOrderedProducts[i] = orderProduct[i];
tempOrderedQuantity[i] = orderQuantity[i];
}
orderProduct = new Product[tempOrderedProducts.length];
orderQuantity = new int[tempOrderedQuantity.length];
for (int i = 0; i < orderQuantity.length; i++) {
orderProduct[i] = tempOrderedProducts[i];
orderQuantity[i] = tempOrderedQuantity[i];
}
orderProduct[productCount] = aProduct;
orderQuantity[productCount] = aQuantity;
productCount++; //you forgot this
}
}
What's more, there is a simple way to deal with array copy:
public void setOrderProduct(Product aProduct, int aQuantity) {
if (productCount == 0) {
orderProduct[0] = aProduct;
orderQuantity[0] = aQuantity;
} else {
Product[] tempOrderedProducts = new Product[orderProduct.length + 1];
int[] tempOrderedQuantity = new int[orderQuantity.length + 1];
//System.arraycopy is more convenient and efficient
System.arraycopy(orderProduct, 0, tempOrderedProducts, 0, orderProduct.length);
System.arraycopy(orderQuantity, 0, tempOrderedQuantity, 0, orderQuantity.length);
//you don't need to copy back, just re-assign the reference
orderProduct = tempOrderedProducts;
orderQuantity = tempOrderedQuantity;
orderProduct[productCount] = aProduct;
orderQuantity[productCount] = aQuantity;
productCount++;
}
}