General part first:
This is for my Java 1 final: I need to make an NFL playoff simulator. So, I would make a "Team" object that holds values for "Offense" and whatnot. I would need a method that holds an algorithm to calculate who wins each matchup. However, I don't know how to go about applying the method to the appropriate teams..
I was going to make another object called "Matchup" which would hold 2 "Team" objects, then comparing the 2 teams' values with the algorithm method. But, I don't think you can use objects inside another object, to my knowledge... Therefore, I've just been trying to hard-code everything in an ugly way.
Would anyone point me in the right direction of forming such a program?
Anyway, on to my immediate issue:
Here is my small bit of code thus far..
public class Final_Larrabee {
static Team pit = new Team("Steelers", "AFC", 3, 75, 70);
static Team bal = new Team("Ravens", "AFC", 6, 70, 80);
static String teamA1 = "bal";
public static void main(String[] args) {
System.out.println(+teamA1.seed);
}
}
And my other class:
package final_larrabee;
public class Team {
String name;
String conference;
int seed;
int offense;
int defense;
boolean wcWin;
boolean divWin;
boolean conWin;
boolean alive;
public Team(String n, String c, int s, int o, int d) {
name = n;
conference = c;
seed = s;
offense = o;
defense = d;
wcWin = false; // these wins will be used in the betting part
divWin = false;
conWin = false;
alive = true; // determines if team is out of playoffs or not
}
public String getName(){
return this.name;
}
public void setName(String n){
name = n;
}
public int getConference(){
return this.seed;
}
public void setConference(String c){
conference = c;
}
public int getSeed(){
return this.seed;
}
public void setSeed(int s){
seed = s;
}
public int getOffense(){
return this.offense;
}
public void setOffense(int o){
offense = o;
}
public int getDefense(){
return this.defense;
}
public void setDefense(int d){
defense = d;
}
}
I realize this won't work, because it is trying to access teanA1's seed value (which doesn't exist of course). But, what I wanted was to simply call the bal.seed value. I wanted to do it this way so that later, I can use teamA1 and teamA2 variables for the 2 teams in a given matchup. Is there a way to do it this way?
If not, perhaps ideally, it would be best to create a Team object called teamA1 which holds the values of whatever team I need at the time. It would need to change like a variable instead of make a million objects every time I need it (ideally..) I found the method 'clone' but I'm not sure this is what I want?
Any help, be it to my immediate question, or the general layout of my program, would be much appreciated. Thanks!
make team implements comparable this will give you the ability to write compareTo method and then you can put you win condition based
Just as your class Final_Larrabee holds 2 team objects in your code, your matchup class can also hold other objects.
Yes, you're on the right track with the idea of creating a matchup class which holds instances of team objects.
Inside your main class you can initialize 2 team objects. I would then create a matchup object, which gets passed the 2 team objects you have previously created and do some functionality.
Inside your team class you could implement a method, which returns a score based on the teams stats. For example it could calculate the offense * defence * seed or something like and return it that and then inside your match class, you can then implement a method such as playGame() which calls the getScore() method of each object and compares the values and then returns the winner (or prints them out for simplicity).
As regards your code, you're using the keyword static. Static is a keyword which changes a variable/object/method to a class variable/object/method. This means that every instance of the class shares this variable. I would not use it for creating the teams. An example of where to use static (a very basic example), would be if for some reason you needed to keep track of the amount of team objects you created. You could implement a static COUNT variable inside the team object and increase it by one every time the constructor is called. This could also be used for assigning IDs to the teams.
static int TEAM_COUNT = 0;
public Team()
{
this.id = ++TEAM_COUNT;
}
This would make the TEAM_COUNT be a value which shared by all instances of the class team. If you were to call
teamA.setTeamCount(0);
Then every other instance of Team would also be reset to 0.
Edit: With regards to your playoffs
public static void main(String args[])
{
Team team1 = new Team("parameters required here");
Team team2 = new Team("parameters required here");
Playoff p = new Playoff();
p.add(team1);
p.add(team2);
p.startPlayoffs();
}
If you create all of the objects inside the main class, then they are available to that method as they are local. When you call p.add(), you can add them to an array or collection, which is inside the Playoff class. Your startPlayoffs() method can then process the array of objects already stored inside the class.
Related
I am learning Java, so I understand this is a very simple question, but I still want to understand it.
I want to let my code automatically generate soldiers, and the number automatically increases, but I failed.
the Soldier.class:
package com.mayer;
import java.util.Random;
public class Soldier {
private int number=0;
private int ATK;
private int HP;
Random ra = new Random();
public Soldier(){
this.number++;
this.ATK = ra.nextInt(10)+90;
this.HP = ra.nextInt(20)+180;
}
public void report(){
System.out.println("number:"+this.number+"\t"+
"ATK:"+this.ATK+"\t"+
"HP:"+this.HP);
}
}
the main.class
package com.mayer;
public class Main {
public static void main(String[] args) {
Soldier[] soldiers = new Soldier[5];
int i = 0;
while(i<5){
soldiers[i] = new Soldier();
i++;
}
for(Soldier sol:soldiers){
sol.report();
}
}
}
That's what I get:
number:1 ATK:94 HP:187
number:1 ATK:94 HP:181
number:1 ATK:96 HP:193
number:1 ATK:90 HP:183
number:1 ATK:95 HP:193
So you see,each of this number is 1.
You have added number field which is instance field. It will initialize per instance. You are looking for static type variable. Please check static into java.
Instance Variables (Non-Static Fields) Technically speaking, objects
store their individual states in "non-static fields", that is, fields
declared without the static keyword. Non-static fields are also known
as instance variables because their values are unique to each instance
of a class (to each object, in other words); the currentSpeed of one
bicycle is independent from the currentSpeed of another.
Class Variables (Static Fields) A class variable is any field declared with the static modifier; this tells the compiler that there
is exactly one copy of this variable in existence, regardless of how
many times the class has been instantiated. A field defining the
number of gears for a particular kind of bicycle could be marked as
static since conceptually the same number of gears will apply to all
instances. The code static int numGears = 6; would create such a
static field. Additionally, the keyword final could be added to
indicate that the number of gears will never change.
The constructor is changed to：
public Soldier(int number){
this.number = number;
this.ATK = ra.nextInt(10)+90;
this.HP = ra.nextInt(20)+180;
}
As others have said, each Soldier instance has its own separate number field which starts with 0. You can use a static field to count the instances:
public class Soldier {
private static int counter = 0;
private int number;
// other fields left out for clarity
public Soldier(){
Soldier.counter++; // field shared among all Soldier instances
this.number = counter; // number belongs to this instance only
// ...
}
// ...
}
However, I wouldn't recommend doing it this way. When you get more advanced, you'll learn that using a static field like this can cause problems in a multi-threaded application. I would instead advise passing the number to the Soldier constructor:
public class Soldier {
private int number;
// ...
public Soldier(int number){
this.number = number;
// ...
}
// ...
}
And then:
public static void main(String[] args) {
Soldier[] soldiers = new Soldier[5];
int i = 0;
while(i<5){
soldiers[i] = new Soldier(i);
i++;
}
Soldier.class
all-uppercase field names tend to be used for constants.. basic fields use headless camel-case.. They should also be descriptive, i.e. you should look at them an it should be apparent what they represent - for example a variable "number" is not a good idea, because it's ambiguous
Random can be converted to a local variable, no need to keep it on the class level
The mechanism by which soldiers are assigned IDs should be on a higher level - it can't be managed by the soldier object itself, hence the constructor with an argument
overriding the toString method is the traditional way of transforming the object to string for debugging purposes.. also most IDEs can generate it with a press of a button so no space for human error
You will obviously need getters and setters for your variables, if you wish to read or change them from elsewhere, but I don't think that's necessary to post here.
private int soldierID;
private int attack;
private int health;
public Soldier(int id){
this.soldierID = id;
Random random = new Random();
this.attack = random.nextInt(10) + 90;
this.health = random.nextInt(20) + 180;
}
#Override
public String toString() {
return "Soldier{" +
"soldierID=" + soldierID +
", attack=" + attack +
", health=" + health +
'}';
}
Main.class
it's perfectly fine and actually preferred to use a List instead of an array, because it's more comfortable to work with
this way it's even much easier to add them dynamically and use the iterator for ID
you can "report" in the creation cycle
This even shortens the method a bit, not that it's that important here.
public static void main(String[] args){
List<Soldier> soldiers = new ArrayList<>();
for(int i=0; i<5; i++){
Soldier newSoldier = new Soldier(i);
soldiers.add(newSoldier);
System.out.println(newSoldier.toString());
}
}
This way when you define the soldier IDs it's not from within the Soldier class but rather from something that is "observing" all the soldier classes and knows which is which.
I have a java program that models a tv and has stuff like power, channel, volume etc. It also has a unique Serial number that is automatically set (increments 1)
However, for my last array item array[2] I need to referernce my array[0] doing this works but my serialNo is no longer unique and just increments 1 (acts like a new tv has been created)
I think your problem lies in the usage of
public static int serialNo() {
return serialNo++;
}
Each time you call this method, you increment the content of the static field.
There is no direct relation between a TV and its serial number.
I suggest that you create a private field serialNumber in the TV class and assign e.g. in the constructor serialNo to serialNumber and then increment.
serialNo is static member of Tv class, this is what Oracle's documentation says about statics.
Fields that have the static modifier in their declaration are called
static fields or class variables. They are associated with the class,
rather than with any object. Every instance of the class shares a
class variable, which is in one fixed location in memory. Any object
can change the value of a class variable, but class variables can also
be manipulated without creating an instance of the class.
In this case, serialNo is not really associated with any object. So, there won't be something like serialNo of the reference at array[2] in this code.
Now, coming back to the question, you have a for loop that increments serial number as shown below:
for (int i = 0; i < tvDetails.length; i++) {
System.out.println(SERIAL_NO + "\t\t" + tvDetails[0].serialNo() + "\n");
It executes tvDetails.length times (3) ad hence, the number gets incremented. If you don't want it to be incremened there then you need to make a couple of changes:
Remove return serialNo++; from serialNo() method and just return serialNo:
public static int serialNo() {
return serialNo;
}
Increment serialNo in Tv's constructor, e.g.:
public Tv(boolean tvPower, int channel, int volumeLevel) {
this.tvPower = tvPower;
this.channel = channel;
this.volumeLevel = volumeLevel;
serialNo++;
}
The problem is here:
public static int serialNo() {
return serialNo++;
}
This violates the SRP, the Single Responsibility Principle, by doing four things:
* Initializes an instance's serialNo,
* Generates a global "next serial no",
* Reports the global serial no, and
* Reports the instance's serial no, impossible for a static member.
Don't use the same name for different things.
public class Tv {
private static int universalSerial; // not thread-safe
public static int getUniversalSerial() {
return universalSerial;
}
static int dispenseUniversalSerial() {
return universalSerial++;
}
private final int serial;
public Tv () {
this.serial = dispenseUniversalSerial();
}
public int getSerial() {
return serial;
}
#Override public boolean equals(Object other) {
if (this == other) { return true; }
if (! (other instanceof Tv)) { return false; }
Tv otherTv = (Tv) other;
return serial == otherTv.serial;
}
#Override public int hashCode() {
return serial;
}
#Override public String toString() {
return "Tv " + serial;
}
}
Notice how the four tasks are split up between static and instance behaviors. Notice how the different names label different things. Notice the elimination of name parts like No that indicate implementation. Notice the coordinated overrides of the Big Three methods, equals, hashCode, and toString. Notice the lack of override for the fourth member of the Big Three, compareTo. That's deliberate. Notice the lack of thread safety. Notice that the instance serial field is final.
All of those decisions have purpose, and are boilerplate for value classes. The example implementation here is bog standard for non-thread-safe, non-comparable value classes with a factory. You should be able to code one of these up in about 10 minutes. It's a great kata to practice it.
Sorry if the title was worded incorrectly, please change it if it's not quite what I describe here.
So I am creating a program to simulate some fictitious creatures, and I need many objects that all store different statistics about each individual creature with values that can all be checked at the same time. What would be the correct way to go about doing this?
For reference, here is the code that I have right now.
public class Model {
static int mfood;
static int mdefense;
static int mattack;
static int mhealth;
static int msize;
static int magg;
static boolean update = false;
public Model(int food, int meat, int defense, int attack, int health, int agg) {
mfood = food;
msize = size;
mdefense = defense;
mattack = attack;
mhealth = health;
magg = agg;
}
The problem is, of course, that I have variables that store the values that are put into the constructor that are changed each time the constructor is called. This works well if I have only one object running at a time, but I will have around a dozen, most likely. These values need to be called in other methods as well, such as
public void Attack() {
mhealth = (mhealth + mdefense) - mattack;
}
The mattack variable would be a different object from the mhealth and mdefense variables.
Thanks for any help I can get, I'm sure this is a simple fix, but I can't find the answer anywhere.
Your variables are static, meaning they exist at the class level, not the individual object level. This means no matter how many objects you create (new up), they all share the same variables. Remove the static keywords and each object will have it's own copy of the variables.
I am running following code in java and have some questions.
I am calling following line in a Test class:
building.floor(3).waitForElevator();
My Building class has following method which returns the floor object from an array (floors) for given floorNumber.
ArrayList<Floor> floors = new ArrayList<Floor>();
public Floor floor(int floorNumber) {
return floors.get(floorNumber);
}
My Floor class has waitForElevator() method. In my Floor class I also have an array of length 7 called passengerWaiting. Whenever waitForElevator() is called, I would like to access the correct floorNumber in passengerWaiting array and change its value.
What I am struggling with is when building.floor(3).waitForElevator() is called, how do I access the index (3 in this example) from Floor class.
Thanks for all the help in advance.
You could store the value in a class instance variable and make it accessible via an accessor.
public class Building{
private int floor = 0;
private ArrayList<Floor> floors = new ArrayList<Floor>();
public Buliding(){
Floor floor1 = new Floor(this);
this.floors.add(floor1);
}
public Floor floor(int floorNumber) {
this.floor = floorNumber;
return floors.get(floorNumber);
}
public int getFloor(){
return floor;
}
}
If you add a constructor for Floor that accepts an instance of building and stores it as an instance variable you can access floor at any time.
public class Floor{
private Building building;
public Floor(Building building){
this.building = building;
}
public void waitForElevator(){
int floor = this.building.getFloor();
}
}
Another Solution
Simply pass the int to waitForElevator as an argument.
public class Floor{
public void waitForElevator(int floor){
System.out.println(floor);
}
}
//Usage
building.floor(3).waitForElevator(3);
Note This solution is not as great because the client could invoke as building.floor(3).waitForElevator(4);
To solve your current problem, I would suggest having each floor keep an int of which floor it is.
However, that seems like code smell to me, so I must ask why you need to do it this way. Could you possibly implement it such that you could just call building.waitForElevator(3)? Another refactoring would be to, rather than have one passengerWaiting ArrayList, have an int value for passengerWaiting in the Floor class, and just change that on each call to waitForElevator.
If you would post your full problem, I could give more helpful of suggestions, I'm guessing here based on the snippets you posted.
I have a task to operate on complex number. Each number consists of double r = real part, double i = imaginary part and String name. Name must be set within constructor, so I've created int counter, then I'm sending its value to setNextName function and get name letter back. Unfortunately incrementing this 'counter' value works only within costructor and then it is once again set to 0. How to deal with that?Some constant value? And second problem is that I also need to provide setNextNames(char c) function that will change the counter current value.
The code :
public class Imaginary {
private double re;
private double im;
private String real;
private String imaginary;
private String name;
private int counter=0;
public Imaginary(double r, double u){
re = r;
im = u;
name = this.setNextName(counter);
counter++;
}
public static String setNextName(int c){
String nameTab[] = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N",
"O","P","Q","R","S","T","U","W","V","X","Y","Z"};
String setName = nameTab[c];
System.out.println("c: "+c);
return setName;
}
public static String setNextName(char c){
//
//don't know how to deal with this part
//
}
It's hard to tell what you're doing, but I suspect this will solve your immediate problem:
private static int counter = 0;
You should make counter static.
You should also make nameTab a private static field, then in setNextName(), you can iterate through it to find the name corresponding to the given character, and get its index. (in the plain ASCII world, of course one could simply calculate the index by subtracting the numeric value of 'A' from the given character, but I am not quite sure how it would work out with Java, in Unicode, with crazy inputs - iteration is on the safe side.)
In OO languages there are typically two types of variables that go into a class:
instance variables that are unique to each instance
class variables that are shared by all instances of the class
Given a class like:
public class Person
{
// class variable
private static int numberOfEyes;
// instance variable
private String name;
// other code goes here
}
If you were to do something like:
Person a = new Person("Jane Doe");
Person b = new Person("John Doe");
and then do something like:
a.setName("Jane Foe");
the name for Person "a" would change, but the one for Person "b" would stay the same.
If you woke up one morning and decided you wanted 3 eyes:
Person.setNumberOfEyes(3);
then Person "a" and Person "b" and every other Person instance out there would suddenly have 3 eyes as well.
You want to put "static" in your counter declaration.
is your code being used by multiple threads than i would suggest that making counter static won't solve ur problem.
you need to take extra care by implementing thread synchronization use lock keyword as shown below.
private static readonly obj = new Object();
private static int counter =0;
public Imaginary(double r, double u)
{
re = r;
im = u;
lock(obj)
{
name = this.setNextName(counter);
counter++;
}
}
this will ensure thread safety also while incrementing your counter (there are another ways also to provide thread security but this one is having least code).
Because the field counter is not static, every object has its own counter.