Topological sorting and cycles

Topological sorting and cycles - java

I've got some input files from my teacher wich we are supposed to test the program with. The task is to read from file, create a directed graph and print out the output. But if there is a cycle we are supposed to terminate the program.
I've got some files named house1 and house2. in the file house1 there isn't any cycles, but in house2 there is. But I can't figure out why my program can't find that cycle.
Here I have all the code, and any help saying where I should be looking at is preciated :)
import java.util.*;
import java.io.*;
import java.lang.*;
class Input {
public static void main(String[] args) {
if (args.length == 0) {
System.out.println("enter a filename!");
System.exit(1);
} else if (args.length == 1) {
String fil = args[0]+".txt";
LesFraFil(fil);
// skrivUt();
topSort();
} else {
System.out.println("too many parameters, try again...");
}
}
static int antTask;
static Task[] ids;
static int tTid;
static void LesFraFil(String fil) {
int i = 0;
int j;
try {
String lest;
Scanner in = new Scanner(new FileReader(fil));
Edge til;
int counter = 0;
antTask = in.nextInt();
ids = new Task[antTask];
System.out.println(antTask);
while (in.hasNextLine()) {
lest = in.nextLine();
// hvis tom linje, så hopper den over
if(lest.trim().length() == 0) continue;
String split[] = lest.split("\\s+");
int id = Integer.parseInt(split[0]);
String act = split[1];
int tid = Integer.parseInt(split[2]);
int staff = Integer.parseInt(split[3]);
int depA = Integer.parseInt(split[4]);
tTid += tid;
ids[i] = new Task(id, act, tid, staff);
j = 4;
/*
* Lesingen av inputen skal avbrytes når den leser 0.
* j er den som holder på hvor langt vi er i split arrayet
* når den møter på 0
*/
while(split[j].compareTo("0") != 0) {
int tmp = Integer.parseInt(split[j])-1;
// System.out.println(tmp+1 + " Aktivitetens navn : " + act); //+ " tiden aktiviteten tar tid: " + tid + " avhengihet: " + split[j]);
j++;
if (ids[tmp] == null) {
ids[tmp] = new Task(id, act, tid, staff);
ids[tmp].visited = true;
}
ids[i].cntPredecessors++;
if(ids[tmp].outEdge == null) {
ids[tmp].outEdge = new Edge(ids[tmp], ids[i]);
} else {
til = ids[tmp].outEdge;
while(til.neste != null) {
til = til.neste;
}
// til.neste = new Edge(ids[tmp], ids[i]);
}
}
counter++;
i++;
}
if (antTask == counter) {
System.out.println("Lesinga gikk som planlagt av fil: " + fil);
System.out.println("Total arbeidstid: " + tTid);// + antTask + " == " + counter );
} else {
System.out.println("Noe gikk galt avslutter!");
System.out.println(antTask + " || " + counter);
System.exit(2);
}
in.close();
} catch (Exception e) {
System.err.println("Dette gikk galt med lesinga: " + e.getMessage());
}
}
static void topSort() {
LinkedList<Task> list = new LinkedList<Task>();
ArrayList<Task> array = new ArrayList<Task>();
Task temp;
int totalTime = 0;
int counter = 0;
for(Task t : ids) {
if (t.cntPredecessors == 0) {
list.add(t);
}
}
while (!list.isEmpty()) {
temp = list.pop();
counter++;
array.add(temp);
System.out.println("Time " + totalTime + "\t Started task " + temp.id + "\t Staff: " + temp.staff + ", Task done " + temp.id);
totalTime += temp.time;
for (Task t : ids) {
if (--t.cntPredecessors == 0)
list.add(t);
}
}
if(counter < antTask) { // checking for loop
System.out.println(counter + " != " + antTask);
System.out.println("En løkke er funnet i grafen. Avslutter...");
System.exit(0);
}
System.out.println("Topological sort: " + Arrays.toString(array.toArray()));// den sorterte "arraylisten"
System.out.println("Total tid brukt er: " + totalTime);
}
}
class Task {
int id, time, staff;
int depA, depB;
String name;
int eStart, lStart;
Edge outEdge;
int cntPredecessors;
boolean visited;
Task(int id, String name, int time, int staff) {
this.id = id;
this.name = name;
this.time = time;
this.staff = staff;
visited = false;
}
public String getName() {
return name;
}
public String toString() {
return name;
}
}
class Edge {
Task fra, til;
Task id, name, time, staff;
Edge neste;
// Task fra, til;
Edge(Task fra, Task til) { //, Task fra, Task til) {//, Task name, Task time, Task staff) {
this.fra = fra;
this.til = til;
// this.id = id;
// this.fra = fra;
// this.til = til;
/* this.name = name;
this.time = time;
this.staff = staff;*/
}
public Task getTil() {
return til;
}
}

I'll write here some kind of simple algorithm, what you are doing is a topological sort
Important thing is that topological sort is using DFS algorithm O(V+E)
What you should do is to create some kind of additional attribute for each Node (let's call it String color and set it's initial value to white.
As you'll iterate through your nodes, set it's color to gray, and continue doing a DFS, after it's done, set it's color to black.
The point is - if you visit a node with color == gray or color == black you found a cycle
I recommend reading a Topological sort chapter from Introduction to Algorithms
And let's see your code!
You read something from input file and important part is here:
while (!list.isEmpty()) {
temp = list.pop();
counter++;
array.add(temp);
System.out.println("Time " + totalTime + "\t Started task " + temp.id + "\t Staff: " + temp.staff + ", Task done " + temp.id);
totalTime += temp.time;
for (Task t : ids) {
if (--t.cntPredecessors == 0) {
list.add(t);
}
}
}
well sorry for saying it like this, but your code is little messy, without english documentation, etc. but I think you are missing the part of coloring your nodes, that can be the reason why you can't find a cycle ( and I suppose you never end ) , because you miss to "color" your nodes, so nobody knows that you have already visited them
btw my "color" attribute is called visited in your code (you can use boolean but then you can't color it to gray/black/white as in the book I posted here)
I guess you set it to true during initialization (you should set it to false and set it to true if you have already processed/visited the node)
// Sorry if I'm wrong but it's 1A.M. here, I just think this might be the issue
// + if you do this on directed graph, and exit if you detect cycle, you get and cycle detection algorithm in O(V) time :)

Related

How to read values from array list from another class and get output depending on user input?

So, I'm trying to figure out how to get values of an array list from another class and print certain values depending on user input.
For example, firstly a user is asked to provide a location, once they enter a location, it has to read the user input and output the results according to the location.an image is provided about the output.
For some reason it doesn't output the correct values from array list.
Could you please help me out?
This is my code for reading values from array list.
public class Program {
ArrayList<Properties> property = Properties.getMelbnbProperty();
int i = 1;
for(i = 1; i < (property.size());) {
System.out.println(property.get(i));
break;
}
ArrayList<Properties> output = Properties.getMelbnbProperty();
if(Properties.getMelbnbProperty().contains(choice)) {
output.addAll(Properties.getMelbnbProperty());
}
} }
This is my code for array list.
public class Properties {
public static ArrayList<Properties> getMelbnbProperty() {
// Below is an arraylist where I have stored the Melbnb data
ArrayList<Properties> property = new ArrayList<Properties>();
property.add(new Properties("Private room in the heart of Southbank"));
property.add(new Properties("Spacious bedroom in a cosy apartment in South Yarra\n"));
property.add(new Properties("Ensuite room with great views"));
property.add(new Properties("Single room next to Carlton Gardens"));
property.add(new Properties("Studio close to Melbourne CBD"));
property.add(new Properties("1-bedroom CBD view suite near Melbourne Central and RMIT"));
property.add(new Properties("Stylish two bedroom in CBD"));
property.add(new Properties("Sky high studio with amazing views"));
property.add(new Properties("Budget accommodation bunk beds"));
property.add(new Properties("A beautiful room near Marvel Stadium"));
return property;
}}

The code you have provided in your question post is incomplete and in a way doesn't make sense to what your image displays. I do however understand what you are trying to accomplish but the way I see it your properties class is somewhat under-nourished.
I don't know if this is the intentional purpose but your for loop:
int i = 1;
for(i = 1; i < (property.size());) {
System.out.println(property.get(i));
break;
}
is designed to pull out 1 object from the property ArrayList. This loop is completely unnecessary since just supplying an index value of 1 to the ArrayList#get() method does exactly the same thing and is only a single line of code, for example:
System.out.println(property.get(1));
I say this because your for loop initializer starts at index 1, there is no iterator for the loop, and you apply the break statement directly after the display of the object within the ArrayList.
To access all elements within the ArrayList (your post indicates) you would need to do something like this:
for (int i = 0; i < properties.size(); i++) {
System.out.println(properties.get(i));
}
Or you can use:
for (String props: properties) {
System.out.println(props);
}
To be honest, what you are showing for code in grossly underdeveloped. I don't want to come across as insulting but it's obvious that you are not showing as much as you should be and therefore it is extremely difficult to provide you with any concrete solution to your problem. For this reason, I think it is just easier to provide you with a working demo console application which would allow you to perhaps grasp some concepts from.
The runnable code below consists of two specific classes, the start up class named SimpleBNBDemo which contains the main() method and the Properties class which allows you to instantiate instances of different BNB properties. As you can see, the Properties class is somewhat more fulfilled than the class you provided in your question post. Take the time to read through the code and try to follow its flow. Do keep in mind, although runnable this is only a Demo application and is in now way a complete works. I personally would never hard-code fill an ArrayList with Object data. This data should come from and or saved to a file system or database. However, for demo purposes this will suffice.
The SimpleBNBDemo class:
public class SimpleBNBDemo {
// Field variables
public final static String LS = System.lineSeparator();
public final static java.util.Scanner USER_INPUT = new java.util.Scanner(System.in);
// class member variable
private Properties prop = new Properties();
private final String line = "------------------------------------------------";
private int pwAttempts = 0;
public static void main(String[] args) {
// Started this way to avoid the need for statics
new SimpleBNBDemo().startApp(args);
}
private void startApp(String[] args) {
/* Create Properties instances...
You can do this with whatever means you like. */
java.util.List<Properties> properties = prop.getProperties();
properties.add(new Properties("Southbank Mannor", "Room", "Private room in the heart of Southbank.", "South", 86.00d, true));
properties.add(new Properties("Yarra House", "Room", "Spacious bedroom in a cosy apartment in South Yarra.", "South", 74.00d, true));
properties.add(new Properties("Ensuite Haven", "Room", "Ensuite room with great views.", "West", 65.50d, true));
properties.add(new Properties("Carlton Place", "Room", "Single room next to Carlton Gardens.", "South", 78.00d, true));
properties.add(new Properties("Melbourne Studio", "Studio", "Studio close to Melbourne CBD.", "East", 78.00d, true));
properties.add(new Properties("Melbourne Delight", "Room", "1-bedroom CBD view suite near Melbourne Central and RMIT.", "North", 135.00d, true));
properties.add(new Properties("CBD House", "Suit", "Stylish two bedroom in CBD.", "West", 100.00d, true));
properties.add(new Properties("Sky-High", "Studio", "Sky high studio with amazing views.", "North", 95.00d, true));
properties.add(new Properties("Budgeteer", "Room", "Budget accommodation bunk beds.", "South", 65.00d, true));
properties.add(new Properties("Stadium House", "Room", "A beautiful room near Marvel Stadium.", "East", 95.00d, true));
println("Welcome to MelBNB" + LS + line);
println();
// Menu 1 - Main Menu
String choice = "";
String[] locations = prop.getAllLocations();
if (locations.length == 0) {
printErr("No BNB's with Location in database yet!");
return;
}
while (choice.isEmpty()) {
println("Select from Main Menu:");
println(" 1) List all Accomodations");
println(" 2) Search by location");
println(" 3) Browse by type of accomodation");
println(" 4) Filter by rating");
println(" 5) Rate an accomodation");
println(" 6) Exit (quit)");
print("Please choose: -> ");
choice = USER_INPUT.nextLine().trim();
// Validate Entry...switch/case works great for input validation.
switch (choice) {
case "1":
listAllAccomodations();
break;
case "2":
searchByLocation();
break;
case "3":
searchByAccomodationType();
break;
case "4":
searchByRating();
break;
case "5":
rateAnAccomodation();
break;
case "6":
break;
case "~admin~":
adminMenu();
break;
case "~admin attempts reset~":
pwAttempts = 0;
println();
break;
default:
println("Invalid Entry (" + choice + ")! Try again..." + LS);
}
// Was 'Exit' (4) selected?
if (choice.equals("6")) {
// Break out of loop to end application.
println(LS + "Thank you for visiting MelBNB, Bye-Bye." + LS);
break;
}
choice = ""; // Reset 'choice' to be empty in order to loop again..
}
}
private void adminMenu() {
String pwrd = "";
while (pwrd.isEmpty()) {
if (pwAttempts >= 3) {
println(LS + "Admin Menu is NOT Available!" + LS + "To many failed "
+ "consecutive password attempts!" + LS + "Only " + pwAttempts
+ " consecutive attempts are allowed." + LS);
return;
}
print(LS + "Please enter Admin Password (c to cancel): --> ");
pwrd = USER_INPUT.nextLine().trim();
if (pwrd.equalsIgnoreCase("c")) {
println();
return;
}
int psum = 0;
for (int i = 0; i < pwrd.length(); i++) {
psum += pwrd.charAt(i);
}
if (psum != 624) {
pwAttempts++;
println("Invalid Password! Try again...");
pwrd = "";
}
}
pwAttempts = 0;
println();
println("***********************************************");
println("*** Administrative options would go here! ***");
println("*** Press Enter To Continue ***");
println("***********************************************");
String nothing = USER_INPUT.nextLine().trim();
}
private void listAllAccomodations() {
println(LS + "All Available Accomodations:");
println("----------------------------");
int cntr = 0;
String underline = "";
for (Properties pp : prop.getProperties()) {
cntr++;
String str = pp.toStringTable(pp, cntr == 1);
underline = String.join("", java.util.Collections.nCopies(str.length(), "="));
println(str);
if (cntr == 15) {
println("<- Press Enter To Continue ->");
String nuthin = USER_INPUT.nextLine().trim();
cntr = 0;
}
}
println(underline + LS);
}
private void searchByLocation() {
String[] locationTypes = prop.getAllLocations();
java.util.Arrays.sort(locationTypes);
String locationChoice = "";
while (locationChoice.isEmpty()) {
println();
println("Select the desired location:");
int i = 0;
for ( ; i < locationTypes.length; i++) {
println(" " + (i + 1) + ") " + locationTypes[i]);
}
println(" " + (i + 1) + ") Cancel");
print("Please choose: -> ");
locationChoice = USER_INPUT.nextLine().trim();
// Validate Entry...
if (!locationChoice.matches("[1-" + (locationTypes.length + 1) + "]")) {
println("Invalid Entry (" + locationChoice + ")! Try again..." + LS);
locationChoice = "";
}
}
if (locationChoice.equals(String.valueOf(locationTypes.length + 1))) {
println();
return;
}
String location = locationTypes[Integer.valueOf(locationChoice)-1];
java.util.List<Properties> p = prop.getPropertiesByLocation(location);
if (p.isEmpty()) {
println("No accomodations available in the " + location + " area!" + LS);
return;
}
String str = "Available accomodation within the " + location + " area:";
println(LS + str);
println(String.join("", java.util.Collections.nCopies(str.length(), "-")));
int cntr = 0;
for (Properties pp : p) {
cntr++;
println(pp.toStringTable(pp, cntr == 1));
}
println(line + LS);
}
private void searchByAccomodationType() {
String[] accTypes = prop.getAllAccomodationTypes();
java.util.Arrays.sort(accTypes);
String accChoice = "";
while (accChoice.isEmpty()) {
println();
println("Select the desired accomodation type:");
int i = 0;
for ( ; i < accTypes.length; i++) {
println(" " + (i + 1) + ") " + accTypes[i]);
}
println(" " + (i + 1) + ") Cancel");
print("Please choose: -> ");
accChoice = USER_INPUT.nextLine().trim();
// Validate Entry...
if (!accChoice.matches("[1-" + (accTypes.length + 1) + "]")) {
println("Invalid Entry (" + accChoice + ")! Try again..." + LS);
accChoice = "";
}
}
if (accChoice.equals(String.valueOf(accTypes.length + 1))) {
println();
return;
}
String acc = accTypes[Integer.valueOf(accChoice)-1];
java.util.List<Properties> p = prop.getPropertiesByAccomodationType(acc);
if (p.isEmpty()) {
println("No accomodation type of " + acc + " is available!" + LS);
return;
}
String str = "Available accomodation that are of type '" + acc + "':";
println(LS + str);
println(String.join("", java.util.Collections.nCopies(str.length(), "-")));
int cntr = 0;
for (Properties pp : p) {
cntr++;
println(pp.toStringTable(pp, cntr == 1));
}
println(line + LS);
}
private void searchByRating() {
String rateChoice = "";
while (rateChoice.isEmpty()) {
println();
println("Enter the desired accomodation rating (1 to 5);");
print( "Enter c to cancel. Desired Rating: --> ");
rateChoice = USER_INPUT.nextLine().trim();
if (rateChoice.equalsIgnoreCase("c")) {
return;
}
// Validate Entry...
if (!rateChoice.matches("[1-5]")) {
println("Invalid Entry (" + rateChoice + ")! Try again..." + LS);
rateChoice = "";
}
}
int rating = Integer.valueOf(rateChoice);
java.util.List<Properties> p = prop.getPropertiesByRating(rating);
if (p.isEmpty()) {
println("No accomodation available with the rating of " + rating + "!" + LS);
return;
}
String str = "Available accomodation with a rating of '" + rating + "':";
println(LS + str);
println(String.join("", java.util.Collections.nCopies(str.length(), "-")));
int cntr = 0;
for (Properties pp : p) {
cntr++;
println(pp.toStringTable(pp, cntr == 1));
}
println(line + LS);
}
private void rateAnAccomodation() {
/* Displayed ratings are always the AVERAGE of all ratings
provided for that particular propety. This is done within
the 'Properties.addRating()' method. For this reason and
for other obvious reasons the Properties List should be
saved to either a file or a database. If this is not done
then all added or modified data will be lost when the
application closes. The Properties List data should NOT
be hard-coded. It should be loaded in when the application
starts and saved to storage when data is added or modified.
*/
String[] pNames = prop.getAllPropertyNames();
String nameToRate = "";
while (nameToRate.isEmpty()) {
println(LS + "Enter the name of the accomodation you want to rate:");
print( "Enter 'c' to cancel. Rating: --> ");
nameToRate = USER_INPUT.nextLine().trim();
if (nameToRate.equalsIgnoreCase("c")) {
return;
}
// Validate Entry............................
if (nameToRate.isEmpty()) {
println("Invalid Entry! You must enter a Name! Try again...");
nameToRate = "";
continue;
}
// Does the name exist in List?
boolean found = false;
for (String name : pNames) {
if (name.equalsIgnoreCase(nameToRate)) {
// Yes it does...
found = true;
break; // Break out of this loop.
}
}
if (!found) {
println("Invalid Entry (" + nameToRate + ")!" + LS
+ "Can not find the name supplied! Try again..." + LS);
nameToRate = "";
}
}
//.................................................
/* If we get to here then the name supplied
(regarless of letter case) is in the List. */
String rateNum = "";
while (rateNum.isEmpty()) {
println();
print("Enter your rating (1 to 5 or 'c' to cancel): --> ");
rateNum = USER_INPUT.nextLine().trim();
if (rateNum.equalsIgnoreCase("c")) {
return;
}
// Validate Entry...
if (!rateNum.matches("[1-5]")) {
println("Invalid Entry (" + rateNum + ")! Try again..." + LS);
rateNum = "";
}
println();
}
// Set the rating.
int rating = Integer.valueOf(rateNum);
for (Properties p : prop.getProperties()) {
if (p.getPropertyName().equalsIgnoreCase(nameToRate)) {
int avgRating = p.getAverageRating();
p.addRating(rating);
println("Your rating of " + rating + " has been added to the accomodation" + LS
+ "named '" + nameToRate + "' which has moved its overall rating" + LS
+ "average from " + avgRating + " to an overall average rating of " +
p.getAverageRating() + "." + LS + "This is based on " +
p.getTotalNumberOfRatingsDone() + " rating(s) on the accomodation." + LS);
}
}
}
public static void println(Object... obj) {
if (obj.length > 0) {
System.out.println(obj[0]);
}
else {
System.out.println();
}
}
public static void printErr(Object... obj) {
if (obj.length > 0) {
System.err.println(obj[0]);
}
else {
System.err.println();
}
}
public static void print(Object... obj) {
if (obj.length > 0) {
System.out.print(obj[0]);
}
else {
System.out.print("");
}
}
}
The Properties class:
public class Properties {
public static java.util.List<Properties> properties = new java.util.ArrayList<>();
private String propertyName;
private String accomodationType;
private String description;
private String location;
private double pricePerDay;
private int averageRating = 0;
private int totalNumberOfRatings;
private boolean available;
// Constructor #1
public Properties() { }
// Constructor #2
public Properties(String propertyName, String accomodationType, String description,
String location, double pricePerDay, boolean available) {
this.propertyName = propertyName;
this.accomodationType = accomodationType;
this.description = description;
this.location = location;
this.pricePerDay = pricePerDay;
this.available = available;
}
// Getters & Setters
public java.util.List<Properties> getProperties() {
return properties;
}
public String getPropertyName() {
return propertyName;
}
public void setPropertyName(String propertyName) {
this.propertyName = propertyName;
}
public String getAccomodationType() {
return accomodationType;
}
public void setAccomodationType(String accomodationType) {
this.accomodationType = accomodationType;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public double getPricePerDay() {
return pricePerDay;
}
public void setPricePerDay(double pricePerDay) {
this.pricePerDay = pricePerDay;
}
public int getAverageRating() {
return this.averageRating;
}
public void addRating(int rating) {
// Rateing is an integer value from 1 to 5.
// Where 1 is Bad and 5 Excellent.
if (rating < 1) { rating = 1; }
else if (rating > 5) { rating = 5; }
int sum = 0, r = 0;
for (Properties p : properties) {
if (p.propertyName.equalsIgnoreCase(this.propertyName)) {
r++;
sum += rating;
}
}
if (sum > 0 && r > 0) {
this.averageRating = sum / r;
}
else {
this.averageRating = rating;
}
this.totalNumberOfRatings++;
}
public boolean isAvailable() {
return available;
}
public void setAvailable(boolean available) {
this.available = available;
}
#Override
public String toString() {
return propertyName + ", " + accomodationType + ", " + description + ", "
+ location + ", " + pricePerDay + ", " + averageRating + ", "
+ available;
}
public String toStringTable(Properties p, boolean... addHeader) {
boolean applyHeader = false;
if (addHeader.length > 0) {
applyHeader = addHeader[0];
}
String symbol = java.util.Currency.getInstance(java.util.Locale.getDefault()).getSymbol();
String header = "", underline = "", ls = System.lineSeparator();
StringBuilder sb = new StringBuilder("");
header = String.format("%-18s %-10s %-50s %-10s %-10s %-8s %-6s%n", "BNB Name",
"BNB Type", "BNB Description", "Location", "Price/Day", "Rating", "Avail.");
underline = String.join("", java.util.Collections.nCopies(header.length(), "=")) + ls;
if (applyHeader) {
sb.append(header).append(underline);
}
String[] desc = p.description.split("\\s+");
java.util.List<String> descTmp = new java.util.ArrayList<>();
StringBuilder sb2 = new StringBuilder("");
for (String str : desc) {
if ((sb2.toString() + " " + str).length() > 50) {
descTmp.add(sb2.toString());
sb2.setLength(0);
}
if (!sb2.toString().isEmpty()) {
sb2.append(" ");
}
sb2.append(str);
}
if (!sb2.toString().isEmpty()) {
descTmp.add(sb2.toString());
}
sb.append(String.format("%-18s %-10s %-50s %-12s " + symbol + "%-10.2f %-7s %-6s",
p.propertyName, p.accomodationType, descTmp.get(0), p.location,
p.pricePerDay, p.averageRating, (p.available ? "Yes" : "No")));
if (descTmp.size() > 1) {
for (int i = 1; i < descTmp.size(); i++) {
sb.append(ls).append(String.format("%-18s %-10s %-50s %-12s %-10s %-7s %-6s",
" "," ", descTmp.get(i), " ", " ", " ", " "));
}
}
return sb.toString();
}
public String[] getAllPropertyNames() {
java.util.List<String> tmp = new java.util.ArrayList<>();
for (Properties prop : properties) {
// Make sure names retrieved are Unique (DISTINCT)
if (!tmp.contains(prop.propertyName)) {
tmp.add(prop.propertyName);
}
}
return tmp.toArray(new String[tmp.size()]);
}
public String[] getAllAccomodationTypes() {
java.util.List<String> tmp = new java.util.ArrayList<>();
for (Properties prop : properties) {
// Make sure accomodations retrieved are Unique (DISTINCT)
if (!tmp.contains(prop.accomodationType)) {
tmp.add(prop.accomodationType);
}
}
return tmp.toArray(new String[tmp.size()]);
}
public java.util.List<Properties> getPropertiesByLocation(String location) {
java.util.List<Properties> tmp = new java.util.ArrayList<>();
for (Properties p : Properties.properties) {
if (p.location.equalsIgnoreCase(location) && !tmp.contains(p)) {
tmp.add(p);
}
}
return tmp;
}
public java.util.List<Properties> getPropertiesByAccomodationType(String accomodationType) {
java.util.List<Properties> tmp = new java.util.ArrayList<>();
for (Properties p : Properties.properties) {
if (p.accomodationType.equalsIgnoreCase(accomodationType) && !tmp.contains(p)) {
tmp.add(p);
}
}
return tmp;
}
public java.util.List<Properties> getPropertiesByRating(int rating) {
java.util.List<Properties> tmp = new java.util.ArrayList<>();
for (Properties p : Properties.properties) {
if (p.averageRating == rating && !tmp.contains(p)) {
tmp.add(p);
}
}
return tmp;
}
public int getTotalNumberOfRatingsDone() {
return this.totalNumberOfRatings;
}
public String[] getAllDescriptions() {
java.util.List<String> tmp = new java.util.ArrayList<>();
for (Properties prop : properties) {
// Make sure descriptions retrieved are Unique (DISTINCT)
if (!tmp.contains(prop.description)) {
tmp.add(prop.description);
}
}
return tmp.toArray(new String[tmp.size()]);
}
public String[] getAllLocations() {
java.util.List<String> tmp = new java.util.ArrayList<>();
for (Properties prop : properties) {
// Make sure locations retrieved are Unique (DISTINCT)
if (!tmp.contains(prop.location)) {
tmp.add(prop.location);
}
}
return tmp.toArray(new String[tmp.size()]);
}
public double[] getAllPerDayPrices() {
java.util.List<Double> tmp = new java.util.ArrayList<>();
for (Properties prop : properties) {
// Make sure locations retrieved are Unique (DISTINCT)
if (!tmp.contains(prop.pricePerDay)) {
tmp.add(prop.pricePerDay);
}
}
// Convert List<Double> to double[]...
double[] prices = new double[tmp.size()];
for (int i = 0; i < tmp.size(); i++) {
prices[i] = tmp.get(i);
}
return prices;
}
}

Minecraft Bukkit coding Type mismatch: cannot convert from element type Object to String

Here is the full code for it:
public void trackAll() {
int north = count(Direction.North) * 25;
int east = count(Direction.East) * 25;
int south = count(Direction.South) * 25;
int west = count(Direction.West) * 25;
if ((north == 0) && (east == 0) && (south == 0) && (west == 0)) {
this.player.sendMessage(ChatColor.RED + "Not a valid tracking compass.");
return;
}
for (Direction direction : Direction.values()) {
int length = count(direction) * 25;
if (length != 0) {
#SuppressWarnings("rawtypes")
Set players = new TreeSet();
for (Player player : Bukkit.getOnlinePlayers()) {
if (this.player.canSee(player)) if ((on(player, direction) & !player.equals(this.player))) {
players.add(player.getDisplayName());
}
}
FancyMessage message = new FancyMessage(direction + " (" + length + "): ").color(ChatColor.DARK_AQUA);
int i = 0;
for (String str : players) {
if (i == players.size() - 1)
message.then(str).color(ChatColor.GRAY).tooltip(ChatColor.GREEN + "Click here to track " + ChatColor.RESET + str + ChatColor.GREEN + ".").command("/track " + ChatColor.stripColor(str));
else {
message.then(str).color(ChatColor.GRAY).tooltip(ChatColor.GREEN + "Click here to track " + ChatColor.RESET + str + ChatColor.GREEN + ".").command("/track " + ChatColor.stripColor(str)).then(", ");
}
i++;
}
message.send(this.player);
}
}
}
And I also have another issue "Type mismatch: cannot convert from element type Object to Block"
public int count(Direction direction, boolean b) {
int length = 0;
#SuppressWarnings("rawtypes")
Set toDelete = new HashSet();
for (int i = 1; i < 10000; i++) {
Block next = this.middle.getRelative(BlockFace.valueOf(direction.toString().toUpperCase()), i);
if (next.getType() == Material.COBBLESTONE) {
length++;
toDelete.add(next); } else {
if (next.getType() == Material.STONE) {
length++;
toDelete.add(next);
toDelete.add(this.middle);
break;
}
length = 0;
toDelete.clear();
break;
}
}
if (b) {
for (Block block : toDelete) {
block.getWorld().playEffect(block.getLocation(), Effect.STEP_SOUND, block.getTypeId());
block.setType(Material.AIR);
}
}
return length;
}
I currently don't have someone that can look over the code I personally do not see the issue but I've been working on it for hours so yeah ;/ Thanks. This code is to do with a Minecraft plugin it's tracking a players location and sending the information to the player that executed the command.

Use
Set<String> players = new TreeSet<>();
and
Set<Block> toDelete = new HashSet<>();

Java array of queues printing out only last element within for loop in print method

I spent several hours working on this and even had my professor look at this and it seems to be printing out just the last element in the for loop. It seems to allows me to add the data structure information and initialize the array queue but it only print out the last element. Here is the sufficient code to assist with the question.
static int MAX;
static final int amount = 6;
static boolean [] openflag;
static queue [] Clinic;
static String [] Doctor;
final static String HEADING = "The clinic moniter of Dylan Rychlik";
public static void Listpaitents( ) {
Paitent[] array;
int queuechoice;
JOptionPane.showMessageDialog(null, "Which doctor would you like to
print?");
String InputString = JOptionPane.showInputDialog(null,Doctor, HEADING,
JOptionPane.QUESTION_MESSAGE);
queuechoice = Integer.parseInt(InputString);
if (openflag[queuechoice -1 ] == false){
JOptionPane.showMessageDialog(null, "Sorry, that doctor is not aviable");
}
else {
//Paitent[] array = null;
int limit;
limit = Clinic[queuechoice -1 ].getSize();
array = Clinic[queuechoice -1 ].toArray();
System.out.println(array[0]);
System.out.println(array[1].Print());
System.out.println(array[2].Print());
//int size = Clinic[queuechoice -1].getSize();
//System.out.println(limit);
int x; String out = " Members of the list are: \n";
// boolean exit = false;
for(x = 0; x < limit; x++) {
out += array[x].Print() + "\n";
//System.out.println(out);
// System.out.println(Clinic[queuechoice].toString() + "\n");
}
System.out.println(limit);
JOptionPane.showMessageDialog(null,out);
}
}
Here this is the array() method in the queue clas
public Paitent[] toArray() {
int x;
Paitent[] Array = new Paitent[Length];
queuenode Current = rear;
for (x = 1; ((Current != null) && (x <= Length));x++) {
Array[x-1] = new Paitent();
Array[x-1].update(Current.info);
Current = Current.next;
// System.out.println( Array[x-1].Print());
}
//System.out.println( Array[x-1].Print());
return Array;
}
Any finally here this is the print method
public String Print() {
String outputString;
outputString = "Paitent: " + "-" + name + "\n" + " Telephone number
telephone + " ID " + ID;
return outputString;
}
Any help you can give is really appreciated. I really have spent hours analyzing the code to come up a solution. Its a bulky program.

Using loops to display specific arraylist objects

So I need to display certain elements in an arraylist that have an integer value of over 7. So far I've written this but I'm struggling to make it work. Can anyone help?
public Diary()
{
jobname = new ArrayList<Job>();
}
public void priority ()
{
int index = 0;
while (index < jobname.size ()) {
Job jobName = jobname.get (index);
index ++;
//if (jobname.get (priority)) {
// System.out.println (jobname);
//}
}
}
This is the Job class that is referred to by the Diary.
public Job(String job, int priorityNum, String day)
{
if (priority < 0 || priority > 10) {
priority = 0;
}
else {
priority = priorityNum;
}
jobname = job;
dueDay = day;
}
public boolean isUrgent()
{
return priority > 7;
}
public String toString ()
{
String s = "";
s += "Job = " + jobname + " \n";
s += "Day Due = " + dueDay + " \n";
s += "Priority = " + priority + " \n";
return s;
}

You need to change your code to the following:
public void priority ()
{
foreach(Job job : jobname){
if (job.getPriority() > 7) {
System.out.println (job);
}
}
}
Secondly, add getPriority() in the Job class that would return the value of priority:
public String getPriority(){
return this.priority;
}

In your situation the best option would be "for each" loop.
It would look like that:
for(Job job: jobname)
{
if(job.isUrgent()) System.out.println(job);
}

Printing out most expensive boat and it's information from an array

I am working on a boat program that has a super class (Boat) and two subclasses (SailBoat, Powerboat) and I must print out all of the boats information and price as well as the most expensive boat and it's information alone. This is the part I am having trouble with since I am not entirely sure how to go about it. Here is what I have so far...
Boat Class:
public class Boat {
String color;
int length;
public Boat() {
color = "white";
length = 20;
}
public Boat(String col, int leng) {
color = col;
length = leng;
}
public boolean setColor(String col) {
if ("white".equals(col) || "red".equals(col) || "blue".equals(col) || "yellow".equals(col)) {
col = color;
return true;
} else {
System.out.println("Error: can only be white, red, blue or yellow");
return false;
}
}
public String getColor() {
return color;
}
public boolean setLength(int leng) {
if (leng < 20 || leng > 50) {
leng = length;
System.out.println("Sail Boats can only be between 20 and 50 feet, inclusively.");
return false;
} else {
return true;
}
}
public int getLength() {
return length;
}
public String toString() {
String string;
string = String.format("Color = " + color + " Length = " + length);
return string;
}
public int calcPrice() {
int price;
price = 5000 + length;
return price;
}
}
PowerBoat Subclass
import java.text.NumberFormat;
public class PowerBoat extends Boat {
int engineSize;
public PowerBoat() {
super();
engineSize = 5;
}
public PowerBoat(String col, int len, int esize) {
this.color = col;
this.length = len;
engineSize = esize;
}
public boolean setEngineSize(int esize) {
if (esize < 5 || esize > 350) {
System.out.println(
"Error: That engine is too powerful. The engine size must be between 1 and 350, inclusively");
esize = engineSize;
return false;
} else {
return true;
}
}
public int calcPrice() {
int price;
price = 5000 + length * 300 + engineSize * 20;
return price;
}
public String toString() {
NumberFormat nf = NumberFormat.getCurrencyInstance();
nf.setMinimumFractionDigits(2);
nf.setMaximumFractionDigits(2);
return super.toString() + " Engine Size = " + engineSize + " Price = " + nf.format(calcPrice());
}
}
SailBoat subclass
import java.text.NumberFormat;
public class SailBoat extends Boat {
int numSails;
public SailBoat() {
numSails = 0;
}
public SailBoat(String col, int leng, int numsail) {
color = col;
length = leng;
numSails = numsail;
}
public boolean setNumSails(int nsails) {
if (nsails < 1 || nsails > 4) {
nsails = numSails;
return false;
} else {
return true;
}
} // end setNumSails
public int getNumSails() {
return numSails;
}
public int calcPrice() {
int price;
price = length * 1000 + numSails * 2000;
return price;
}
public String toString() {
NumberFormat nf = NumberFormat.getCurrencyInstance();
nf.setMinimumFractionDigits(2);
nf.setMaximumFractionDigits(2);
return super.toString() + "Color: " + color + " Length: " + length + " Number Sails = " + numSails + " Cost = "
+ nf.format(calcPrice());
}
public int getTotalCost() {
int totalCost = 0;
totalCost += calcPrice();
return totalCost;
}
}
Inventory class (tester)
import java.util.ArrayList;
public class Inventory {
public static void main(String[] args) {
// boat objects
Boat pb1 = new PowerBoat("blue", 22, 60);
Boat sb1 = new SailBoat("white", 20, 1);
Boat sb2 = new SailBoat("red", 42, 3);
Boat pb2 = new PowerBoat("yellow", 35, 80);
Boat pb3 = new PowerBoat("red", 50, 120);
Boat sb3 = new SailBoat("blue", 33, 2);
Boat pb4 = new PowerBoat("white", 20, 10);
ArrayList<Boat> AL = new ArrayList<Boat>();
// add boat objects to arraylist
AL.add(pb1);
AL.add(sb1);
AL.add(sb2);
AL.add(pb2);
AL.add(pb3);
AL.add(sb3);
AL.add(pb4);
// print all boat objects
System.out.println("Print all boats");
for (Boat anyBoat : AL) {
System.out.println(anyBoat.toString());
}
int max = 0;
int totalcost = 0;
Boat mostExpensiveBoat = null;
for (Boat anyBoat : AL) {
if (anyBoat instanceof SailBoat) {
totalcost += anyBoat.calcPrice();
if (anyBoat.calcPrice() > max) {
max = anyBoat.calcPrice();
mostExpensiveBoat = anyBoat;
}
}
}
}
}
I am really confused on how to finish up this program, the results I am supposed to get after all the boat information is printed is this..
Total price of all boats is $ 170,500.00
Most Expensive Boat: Color = red Length = 42 Number Sails = 3 Cost = $ 48,000.00
Any help will be greatly appreciated. Thank you.

There are a few design flaws you should correct:
Your Boat class should be an interface or abstract. You can't have a boat that isn't a power boat or sail boat so you should not be able to instantiate one.
Your instance variables should be private.
Make methods abstract that need to be defined by subclasses of Boat (e.g. calcPrice).
If you are able to use Java 8 then there's a nice way of getting the most expensive boat. The following code will print the most expensive boat (using Boat.toString) if one is present.
allBoats.stream()
.max(Comparator.comparingInt(Boat::calcPrince))
.ifPresent(System.out::println);
That avoids having to write the code that manually iterates through your list comparing prices. It also copes with the situation of an empty list (which means there is no maximum). Otherwise you need to initialise to null and compare to null before printing.

Your for loop should look like this:
for (Boat anyBoat : AL) {
totalcost += anyBoat.calcPrice();
if (anyBoat.calcPrice() > max) {
max = anyBoat.calcPrice();
mostExpensiveBoat = anyBoat;
}
}
It doesn't matter if it's a sailBoat or not, you just wanna print the information of the most expensive one, so you can remove the instanceof condition. After that:
NumberFormat nf = NumberFormat.getCurrencyInstance();
nf.setMinimumFractionDigits(2);
nf.setMaximumFractionDigits(2);
System.out.println("Total price of all boats is " + nf.format(totalcost));
System.out.println("Most expensive boat: " + mostExpensiveBoat.toString());
Should work, since you have already overriden the toString() methods.
one more thing: In your SailBoat toString() method, you are doing:
return super.toString() + "Color: " + color + " Length: " + length + " Number Sails = " + numSails + " Cost = "
+ nf.format(calcPrice());
When you call the super.toString() you are printing the color and the length twice; just call
return super.toString() + " Number Sails = " + numSails + " Cost = " + nf.format(calcPrice());

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