This one should be fairly simple I think, I just can't remember how, when using get methods of an object, how to pull the highest double out of the pack and put it in the println.
So far I just get every object to print with its percentages. But for the life of me I just can't remember and I know I've done this before.
public void displayBookWithBiggestPercentageMarkup(){
Collection<Book> books = getCollectionOfItems();
Iterator<Book> it = books.iterator();
while(it.hasNext()){
Book b = it.next();
double percent = b.getSuggestedRetailPriceDollars() / b.getManufacturingPriceDollars() * 100.0;
System.out.println("Highest markup is " + percent + " " + b.getTitle() + " " + b.getAuthor().getName().getLastName());
}
}
I'm pretty sure I need another local variable but I can't seem to do anything but make it equal the other percent. I have removed the other variable for now as I try to think about it.
I won't go into a lot of detail because it's homework (well done for being up-front about that, by the way) but here's the key idea: keep track of the largest percentage you've seen so far as your loop runs. That's what you want in your other variable.
Good job posting what you've tried so far. You were on the right track. As you loop through your books, keep a variables continuously updated with the highest percent seen so far and another variable for the associated book. Output the variable at the end outside the loop after iteration is done. Also, don't forget to check the edge case of an empty list of books! Something like this should do the trick:
public void displayBookWithBiggestPercentageMarkup(){
Collection<Book> books = getCollectionOfItems();
if (books.size() == 0) {
return;
}
Iterator<Book> it = books.iterator();
double highestPercent = 0;
Book highestPercentBook = null;
while(it.hasNext()){
Book b = it.next();
double percent = b.getSuggestedRetailPriceDollars() / b.getManufacturingPriceDollars() * 100.0;
if (percent > highestPercent) {
highestPercent = percent;
highestPercentBook = b;
}
}
System.out.println("Highest markup is " + highestPercent
+ " " + highestPercentBook.getTitle()
+ " " + highestPercentBook.getAuthor().getName().getLastName());
}
Related
I don't event know how to describe this weird behaviour i'm dealing with right now, but the thing is:
I have a class Player.java that has a private float life, pretty basic.
this float has its setter / getter and there is NO other way of retrieving / attributing this variable without using the getter / setter.
also, i have put a println in each, so i can have a feedback of when this variable is being retrieved, and when is beign attributed, and i get THIS on my console:
my console
i don't think the stack trace is usefull in any way, but if you want to, i can paste the code behind the stack trace too
anyway, if you haven't notice, there is a retrieve of life = 61, FOLLOWED by a retriving of life = 70, with NO attribution WHATSOEVER of this variable back to 70.
also, i dont know if this is useful, but here is the code that prints the "1 damaged 0, broadcasting to clients - Sent":
it resume in:
- decreases the player life
- if it has died, mark as dead and do other little effect things
- send event to google analytics
- after all that, if the game is a server, broadcast the damage event to all clients
public void takeDamage(float amount, Player owner, boolean showBlood, boolean local){
if(local && KambojaMain.getInstance().multiplayerConnection && !KambojaMain.getInstance().isServer) return;
if(imunity <= 0){
//new Exception().printStackTrace();
setLife(getLife() - amount * def);
if(owner != null) {
owner.score += amount*def;
}
if(showBlood)
state.showBlood(body.getWorldCenter());
System.out.println(" - DAMAGE DETECTED from " + owner.getId() + " to " + getId() + " with value " + amount + ", it was a local? " + local + ", and show blood is: " + showBlood);
System.out.println("target life is now at " + getLife());
hitTimer = 1f;
if(getLife() <= 0){
if(!isDead()){
deaths++;
if(owner != null){
owner.kills ++;
owner.ghosts.add(new Ghost(getId(), getPosition()));
owner.score += 100;
}
setDead(true);
body.getFixtureList().get(0).setSensor(true);
getState().showSkull(body.getWorldCenter(), getAngle());
String playerType = "controller";
if(isKeyboard()) {
playerType = "keyboard";
}
if(this instanceof BetterBot) {
playerType = "bot";
}
HashMap<String, String> customs = new HashMap<String, String>();
customs.put("cd1", KambojaMain.getMapName());
customs.put("cd3", getWeapon().getClass().getSimpleName());
customs.put("cd4", "player_" + playerType);
String ow = "Suicide";
if(owner != null)
ow = owner.getWeapon().getClass().getSimpleName();
KambojaMain.event("game", "player_kill", ow, customs);
}
}
if(gruntTimer < 0){
if(GameState.SFX)
grunt[(int)(Math.random()*5)].play();
gruntTimer = 0.5f;
}
if(KambojaMain.getInstance().multiplayerConnection && KambojaMain.getInstance().isServer) {
KambojaPacket kp = new KambojaPacket(PacketType.PLAYER_DAMAGE);
PlayerDamage pd = new PlayerDamage();
pd.damage = amount;
pd.showBlood = showBlood;
pd.owner = owner.getId();
pd.target = getId();
kp.data = pd;
System.out.print(pd.owner + " damaged " + pd.target + ", broadcasting to clients - ");
KambojaMain.getInstance().broadcast(kp, Protocol.TCP);
System.out.println("Sent");
}
}
}
note: i AM using multi threading environment because this is a lan multiplayer game, and this variable can be retrieved in other threads different from the main thread.
I have searched about the volatile keyword, Atomic classes (AtomicFloat dont exist, and the implementation of it using AtomicInt as a bit data also was used), but none of this could prevent this from happening and i have NO idea of what is this behaviour and what is causing it
can someone please help me? i don't know what to search anymore
Try making your method synchronized (this would make sure only one thread can be running this method, on an instance of your class).
public synchronized void takeDamage(.... // same as before
Check out this post, it has a similar question with more info about running blocks of code atomically.
My issue is with the following code. Eclipse IDE gives me no errors or warnings, yet when I print out a simple System.out.println("Test" + i);, I would get a running program up to the number 2509, or currently 2517 after rebooting Eclipse.
Essentially, I want to take an array of objects, say an array of "persons," and place them in random spots in another object array, say "bus stops." Assume that I have properly made the object arrays for "busStops and "people"
Yes, I realize that it defeats the purpose of making the "person" object as of yet, but that is something that can be included later.
Edit: Null values are simulated areas where people can't go, like a lake.
Edit2: replaced for with while loop, replaced decremented i with continue keyword.
Edit3: added more of the methods to elaborate the imperfections of my code. Then again, maybe most of it is good and I'm not understanding something important about loops.
private static void distributePeople() {
boolean temp = true;
int i = 0;
while (temp) {
// Select random points in array
int a = rand.nextInt(busStops.length);
int b = rand.nextInt(busStops[0].length);
// At random busStop, check if available and check if not full.
// If it is not full, place a person there.
if (busStops[a][b] == null) {
// if null, reset this run
continue;
} else {
if (busStops[a][b].isMaxPeople() == false) {
busStops[a][b].setNumberOfPeople(1);
i++;
System.out.println("Test: " + i);
} else {
// if true, reset this run
continue;
}
}
if (i == people.length) {
temp = false;
}
}
}
private static void setMaxPeopleAtBusStop() {
busStops[0][0].setMaxNumberOfPeople(1977 + 2);
busStops[1][0].setMaxNumberOfPeople(2 + 1643);
busStops[2][0].setMaxNumberOfPeople(1643 + 1201);
busStops[3][0].setMaxNumberOfPeople(1201 + 1267);
busStops[0][1].setMaxNumberOfPeople(366 + 0);
busStops[2][1].setMaxNumberOfPeople(0 + 797);
busStops[3][1].setMaxNumberOfPeople(797 + 34);
busStops[0][2].setMaxNumberOfPeople(1740 + 0);
busStops[2][2].setMaxNumberOfPeople(0 + 1444);
busStops[3][2].setMaxNumberOfPeople(1444 + 1963);
busStops[0][3].setMaxNumberOfPeople(839 + 1131);
busStops[1][3].setMaxNumberOfPeople(1131 + 1092);
busStops[2][3].setMaxNumberOfPeople(1092 + 912);
busStops[3][3].setMaxNumberOfPeople(912 + 1965);
busStops[0][4].setMaxNumberOfPeople(1552 + 1297);
busStops[1][4].setMaxNumberOfPeople(1297 + 1345);
busStops[2][4].setMaxNumberOfPeople(1345 + 614);
busStops[3][4].setMaxNumberOfPeople(614 + 1108);
busStops[0][5].setMaxNumberOfPeople(1490 + 228);
busStops[1][5].setMaxNumberOfPeople(228 + 187);
busStops[2][5].setMaxNumberOfPeople(187 + 906);
busStops[3][5].setMaxNumberOfPeople(906 + 36);
busStops[0][6].setMaxNumberOfPeople(634 + 1293);
busStops[1][6].setMaxNumberOfPeople(1293 + 0);
busStops[3][6].setMaxNumberOfPeople(0 + 1929);
busStops[0][7].setMaxNumberOfPeople(759 + 388);
busStops[1][7].setMaxNumberOfPeople(388 + 0);
busStops[3][7].setMaxNumberOfPeople(0 + 1149);
busStops[0][8].setMaxNumberOfPeople(1809 + 1880);
busStops[1][8].setMaxNumberOfPeople(1880 + 1979);
busStops[2][8].setMaxNumberOfPeople(1979 + 954);
busStops[3][8].setMaxNumberOfPeople(954 + 1332);
busStops[0][9].setMaxNumberOfPeople(1890 + 408);
busStops[1][9].setMaxNumberOfPeople(408 + 1771);
busStops[2][9].setMaxNumberOfPeople(1771 + 587);
busStops[3][9].setMaxNumberOfPeople(557 + 1961);
}
From the appropriate BusStop class:
static int MAX_PEOPLE_HERE;
public int setNumberOfPeople(int a) {
return numberOfPeopleHere += a;
}
protected boolean isMaxPeople() {
if (numberOfPeopleHere >= MAX_PEOPLE_HERE) {
return true;
} else {
return false;
}
}
public void setMaxNumberOfPeople(int a) {
MAX_PEOPLE_HERE = a;
}
Note: I should have a max number of 13000 people, which is smaller than the room available above.
Ok so your problem is that you're using a static variable for MAX_PEOPLE_HERE but you're trying to use it in a non static way. Thus ever time you call setMaxNumberOfPeople on any bus stop you set it for all bus stops.
This means that MAX_PEOPLE_HERE will end up being 557 + 1961 = 2518.
I'm guessing that numberOfPeopleHere is also static and thus you can only ever 2518 people to bus stops. If you try to do more than this then you'll end up with an infinite loop as you are seeing.
Change both MAX_PEOPLE_HERE (rename this to maxPeopleHere) and numberOfPeopleHere to local instance variables and I suspect everything will start working.
Use continue instead of i-- to skip current iteration. As #Hovercraft Full Of Eels stated, you've got infinite loop because of index modification within the loop
Let's say i have an OptimizationModel abc.lp, which i want to import with the CPlex java-API. I use: importModel function (click) to import it. Now i want to change some decision variable's factors in the constraint or in the objective. For example the imported model abc.lp looks as follows:
Objective: Minimize <factor1>x1 + <factor2>x2
Constraint: <factor1>x1 + <factor2>x2 <= 40
For me factor1 and factor2 are input parameters of a function. So i get:
public void(double factor1, double factor2){
...
cplexModel.import("path/to/abc.lp")
// Change parameters, how to do it?
Is there a handy way to set the factors dynamically from an imported Model with the Cplex-API?
Thanks a lot!
Yes, this is possible. It's not very intuitive, at least to me.
Here's an example snippet that assumes a LP (linear objective and constraints):
// Read model from file with name args[0] into cplex optimizer object
cplex.importModel(args[0]);
// Get the objective and modify it.
IloObjective obj = cplex.getObjective();
IloLinearNumExpr objExpr = (IloLinearNumExpr) obj.getExpr();
IloLinearNumExprIterator iter = objExpr.linearIterator();
// Loop through the linear objective and modify, as necessary.
while (iter.hasNext()) {
IloNumVar var = iter.nextNumVar();
System.out.println("Old coefficient for " + var + ": " + iter.getValue());
// Modify as needed.
if ( var.getName().equals("x1") ) {
iter.setValue(42);
System.out.println("New coefficient for " + var + ": " + iter.getValue());
}
}
// Save the changes.
obj.setExpr(objExpr);
// Assumes that there is an LP Matrix. The fact that we used
// importModel() above guarantees that there will be at least
// one.
IloLPMatrix lp = (IloLPMatrix) cplex.LPMatrixIterator().next();
for (int i = 0; i < lp.getNrows(); i++) {
IloRange range = lp.getRange(i);
System.out.println("Constraint " + range.getName());
IloLinearNumExpr conExpr = (IloLinearNumExpr) range.getExpr();
IloLinearNumExprIterator conIter = conExpr.linearIterator();
// Loop through the linear constraints and modify, as necessary.
while (conIter.hasNext()) {
IloNumVar var = conIter.nextNumVar();
System.out.println("Coefficient for " + var + ": " + conIter.getValue());
// Modify as needed (as above).
if ( var.getName().equals("x1") ) {
conIter.setValue(42);
System.out.println("New coefficient for " + var + ": " + conIter.getValue());
}
}
// Save changes (as above).
range.setExpr(conExpr);
}
cplex.exportModel("modified.lp");
// Solve the model and display the solution if one was found
if ( cplex.solve() ) {
// do something here.
}
Here, we're looking for a variable named "x1". We set it's coefficient to 42 in the objective and in all linear constraints. The println's are for debugging. I did this quickly, so make sure you test it. Otherwise, you should be able to modify that to suit your needs. Hope that helps.
I have an ArrayList called participatingUsers. Person has Person.money and Person.name that are interesting.
What I want to do is check the ArrayList against itself...
So I have this code
for (Person debtHaver : this.participatingUsers) {
// If they're in debt...
if (debtHaver.getMoney() < 0) {
// With someone...
for (Person personToPay : this.participatingUsers) {
// That's not themselves...
if (!debtHaver.getName().equals(personToPay.getName())) {
// See if the personToPay is ranked higher than the
// debtHaver...
if (personToPay.getMoney() > 0) {
// If the debtee can pay the debter in full
if (-debtHaver.getMoney() <= personToPay.getMoney()) {
payment += debtHaver.getName() + " has to pay " + personToPay.getName() + " " + -debtHaver.getMoney() + "\n";
debtHaver.increaseMoney(-debtHaver.getMoney());
personToPay.decreaseMoney(-debtHaver.getMoney());
}
if (-debtHaver.getMoney() > personToPay.getMoney())
{
//But if he can't pay in full... Just pay the small bit you can pay.
payment += debtHaver.getName() + " has to pay " + personToPay.getName() + " " + personToPay.getMoney() + "\n";
debtHaver.increaseMoney(personToPay.getMoney());
personToPay.decreaseMoney(personToPay.getMoney());
}
}
}
}
}
}
return payment;
Basically, I have a double for loop where I check each person against itself. If someone is in debt and has a negative amount of money, seek if there is someone who they can pay, then pay that person. The thing is, personToPay is not being updated in the arrayList debtHaver is in. I'm basically editing two different ArrayLists instead of the same one. What's the best way to deal with this issue?
You are editing the same list. The problem is probably in this code:
debtHaver.increaseMoney(-debtHaver.getMoney());
personToPay.decreaseMoney(-debtHaver.getMoney());
You are putting debtHaver's amount to zero by the first line. And then you try to modify personToPay with zero amount. Just swap two lines of code and it should work:
personToPay.decreaseMoney(-debtHaver.getMoney());
debtHaver.increaseMoney(-debtHaver.getMoney());
I'm new to OO programing and having a bit of trouble with the design of my program to use the concepts. I have done the tutorials but am still having problem.
I have a recursion that takes a value of items(could be anything in this example, stocks) and figures out what number of them are needed to equal a specific value(in this code 100). This part works but I want to know if a stock's weighting exceeds a threshold. Originally I approached this problem with a method that did a for loop and calculated the entire list of values but this is super inefficient because its doing it on every loop of the recursion. I thought this would be a good time to try to learn classes because I could use a class to maintain state information and just increment the value on each loop and it'll let me know when the threshold is hit.
I think I have the code but I don't fully understand how to design this problem with classes. So far it runs the loop each step of the recursion because I'm initially the class there. Is there a better way to design this? My end goal is to be notified when a weighting is exceeded(which I can somewhat already do) but I want to do in way that uses the least bit of resources(avoiding inefficient/unnecessary for loops)
Code(Here's the entire code I have been using to learn but the problem is with the Counter class and its location within the findVariables method):
import java.util.Arrays;
public class LearningClassCounting {
public static int[] stock_price = new int[]{ 20,5,20};
public static int target = 100;
public static void main(String[] args) {
// takes items from the first list
findVariables(stock_price, 100, new int[] {0,0,0}, 0, 0);
}
public static void findVariables(int[] constants, int sum,
int[] variables, int n, int result) {
Counter Checker = new Counter(stock_price, variables);
if (n == constants.length) {
if (result == sum) {
System.out.println(Arrays.toString(variables));
}
} else if (result <= sum){ //keep going
for (int i = 0; i <= 100; i++) {
variables[n] = i;
Checker.check_total_percent(n, i);
findVariables(constants, sum, variables, n+1, result+constants[n]*i);
}
}
}
}
class Counter {
private int[] stock_price;
private int[] variables;
private int value_so_far;
public Counter(int[] stock_price, int[] variables) {
this.stock_price = stock_price;
this.variables = variables;
for (int location = 0; location < variables.length; location++) {
//System.out.println(variables[location] + " * " + stock_price[location] + " = " + (variables[location] * stock_price[location]) );
value_so_far = value_so_far + (variables[location] * stock_price[location]);
}
//System.out.println("Total value so far is " + value_so_far);
//System.out.println("************");
}
public void check_total_percent(int current_location, int percent) {
// Check to see if weight exceeds threshold
//System.out.println("we are at " + current_location + " and " + percent + " and " + Arrays.toString(variables));
//System.out.println("value is " + stock_price[current_location] * percent);
//formula I think I need to use is:
if (percent == 0) {
return;
}
int current_value = (stock_price[current_location] * percent);
int overall_percent = current_value/(value_so_far + current_value);
if (overall_percent > 50 ) {
System.out.println("item " + current_location + " is over 50%" );
}
}
}
What you're describing sounds like a variant of the famous knapsack problem. There are many approaches to these problems, which are inherently difficult to calculate.
Inherently, one may need to check "all the combinations". The so-called optimization comes from backtracking when a certain selection subset is already too large (e.g., if 10 given stocks are over my sum, no need to explore other combinations). In addition, one can cache certain subsets (e.g., if I know that X Y and Z amount to some value V, I can reuse that value). You'll see a lot of discussion of how to approach these sort of problems and how to design solutions.
That being said, my view is that while algorithmic problems of this sort may be important for learning how to program and structure code and data structures, they're generally a very poor choice for learning object-oriented design and modelling.