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Exit Code 0 instead of printing?

I have the following java code written and when I run it it says: "Process finished with exit code 0" instead of printing totalNumCars(). Why is this, and how do I fix it?
public class ParkingGarage extends Module5{
public int numAutomobiles;
public int numLargeAutomobiles;
public static int numGarages;
public ParkingGarage(int automobiles, int largeAutomobiles){
numAutomobiles = automobiles;
numLargeAutomobiles = largeAutomobiles;
numGarages++;
}
public void addCars(int newAutomobiles, int newLargeAutomobiles){
numAutomobiles += newAutomobiles;
numLargeAutomobiles += newLargeAutomobiles;
}
public int totalNumCars(){
int totalCars = numLargeAutomobiles + numAutomobiles;
return totalCars;
}
public static void main(String[] args){
ParkingGarage garage1 = new ParkingGarage(5,5);
garage1.addCars(5, 5);
System.out.println("Number of Cars: " + garage1.totalNumCars());
}
}

troubles with creating objects in java

Hello So I have a entire class called tractor with different data's stored in it but now I'm suppose to create an object call tractor with a zero parameter constructor but This is the code I have so far and its giving em errors
First off this my Tractor Class which is in a different file:
import java.util.Scanner;
class Tractor
{
private int RentalRate;
private int RentalDays;
private int VehicleID;
private int RentalProfit;
public void setRentalRate(int r)
{
Scanner input = new Scanner(System.in);
System.out.println("What's the Rental Rate?");
int num = input.nextInt();
num = r;
if(r<0 || r >1000)
RentalRate = r;
RentalRate= 1;
}
public int getRentalRate()
{
return RentalRate;
}
public void setVehicleID(int v)
{
Scanner input = new Scanner(System.in);
System.out.println("What's the vehicleID?");
int num1 = input.nextInt();
num1 = v;
if(v<0)
VehicleID = v;
VehicleID = 1;
}
public int getVehicleID()
{
return VehicleID;
}
public void setRentalDays(int d)
{
Scanner input = new Scanner(System.in);
System.out.println("How many rental days?");
int num2 = input.nextInt();
num2 = d;
if(d<0)
RentalDays = d;
RentalDays = 1;
}
public int getRentalDays()
{
return RentalDays;
}
public String toString()
{
String str;
str = "RentalDays:" + RentalDays +"\nRenalRate:" + RentalRate + "\nVehicleID " + VehicleID;
return str;
}
public void RentalProfit(int RentalRate, int RentalDays)
{
RentalProfit = RentalRate * RentalDays;
}
}
import java.util.Scanner;
public class testTractor
{
public static void main(String[] args)
{
public tractor()
{
this.RentalDays = d;
this.RentalRate = r;
this.VehicleID = v;
}
}
}
The error is :
testTractor.java:7: error: illegal start of expression
public tractor()
^
testTractor.java:7: error: ';' expected
public tractor()
^
2 errors

You have compilation errors. You need to first declare the Tractor class then add the constructor inside it. One way to do is declare in a separate file. Also in Java unless you had defined d you couldnt have assigned it. Maybe you wanted to assign the day as a String look in the examples I provide below.
You need to to first create a file call Tractor.java and then define variables there. For example contents of Tractor.java:
public class Tractor {
String rentaldays,someOtherValue;
public Tractor(){
rentaldays ="monday";
someOtherValue="value";
}
//or
public Tractor(String rentalDays){
this.rentaldays = rentalDays;
someOtherValue = "asf";
}
}
Then in your main method You can do Tractor trac = new Tractor(); or Tractor trac = new Tractor("tuesday"); also after that you can print the rentaldays of trac using System.out.println(trac.rentaldays);
From the looks of it you will probably be making a tractor rental system. In that case, rentalDays may be an array of Strings. And then you would have an array of Tractor objects to store in the rental system. You can look at these terms and keywords to point you in the right direction.

You are defining it wrong, define your methods inside class then call them in main() method.
class Test{
public void greeting(){
System.out.print("hello to JAVA..");
}
public static void main(String[] args){
Test testObj = new Test();
testObj.greeting();
}
}

you use an illegal of java syntax, if you already have class tractor in your project. for calling it to in other class, try below code
public class TestTractor(){
Tractor objTractor;
public static void main(String[] args){
//create new tractor object with no parameter
objTractor = new Tractor();
//create new tractor object with parameter
objTractor = new Tractor(parameter here);
//do some action of object here
...........
}
}

//This is just a sample
in your tractor class add below code
public tractor()
{
this.RentalDays = d;
this.RentalRate = r;
this.VehicleID = v;
}
And keep your TestTractor class as
public class TestTractor(){
public static void main(String[] args){
Tractor objTractor = new Tractor();
// objTractor.yourMethodName
}
}

Count number of existing objects

So I'm making a die class that can create and roll a die, return the value and the size. I'm trying to figure out how to tell the program how many of them have been created so that I can have a response be different based on how many there are. IE I want the response from printDie to be Die Value: 5 if there is only one die, and Die 1 Value: 5 if there is more than one.
Here's my code so far.
package com.catalyse.die;
import java.util.Random;
public class Die
{
// instance variables
private int myDieValue;
private int myDieSides;
private Random myRandom;
// Dice Class Constructors
public Die()
{
this.myDieValue = 1;
this.myDieSides = 4;
}
public Die(int numSides)
{
if ((numSides < 4) || (numSides > 100)) {
System.out.println("Error! You cannot have more than 100 sides or less than four!");
System.exit(0);
}
else {
myDieSides = numSides;
}
}
// getter methods
public int getDieSides()
{
return myDieSides;
}
public int getDieValue()
{
return myDieValue;
}
// setter methods
private void setDieSides(int newNumSides)
{
myDieSides = newNumSides;
}
public void rollDie()
{
Random rand = new Random();
int i = (rand.nextInt(myDieSides) + 1);
myDieValue = i;
}
public void printDie(int dieNum)
{
if (dieNum == 1) {
System.out.println("Die Value: "+myDieValue);
}
else {
System.out.println("Die "+dieNum+" Value: "+myDieValue);
}
}
}

You can have static field in your class which could be incremented in the constructor always. The reason why is it should be static is because, static fields are shared by all instances of a class, thus a local copy of the field won't be created for each of the instances you create.
private static int counter = 0;
public Die()
{
counter++;
// Other stuffs
}
// Have a getter method for the counter so that you can
// get the count of instances created at any point of time
public static int getCounter() {
return counter;
}
And then you can call the above method in your calling method like this
void someMethodInAnotherClass() {
int instanceCount = Die.getCounter(); // You need to call static method using the Class name
// other stuffs.
}

Use an static member, that is a 'class' variable, not a 'instance' variable:
private static int count = 0;
In the constructor:
public Die()
{
count++;
this.myDieValue = 1;
this.myDieSides = 4;
}
And a getter:
public static int getCount() {
return count;
}

Use a static variable
public class Die{
static int dieCount = 0;
public Die(){
dieCount++;
}
}
Every time a Die object is created, the count will increase
public static void main(String[] args){
Die die1 = new Die();
Die die2 = new Die();
int count = Die.dieCount;
}

See what is my solution for counting objects in my application
import java.util.Map;
import java.util.TreeMap;
public abstract class ObjectCounter {
private static Map<String, Long> classNameCount = new TreeMap<String, Long>();
public ObjectCounter() {
String key = this.getClass().getName();
if (classNameCount.containsKey(key)) {
classNameCount.put(key, classNameCount.get(key) + 1);
} else {
classNameCount.put(key, 1L);
}
}
public static <T extends ObjectCounter> long getCount(Class<T> c) {
String key = c.getName();
if (classNameCount.containsKey(key)) {
return classNameCount.get(key);
} else {
return 0;
}
}
public static long totalObjectsCreated() {
long totalCount = 0;
for (long count : classNameCount.values()) {
totalCount += count;
}
return totalCount;
}
}
Now extends ObjectCounter class
See below
package com.omt.factory;
public class Article extends ObjectCounter {
}
Now all your other classes are extending Article classes
package com.omt.factory;
public class Bio extends Article {
}
Now here is our main class
package com.omt.factory;
public class Main {
public static void main(String... a) {
Bio b = new Bio();
Bio b1 = new Bio();
Bio b2 = new Bio();
Bio b3 = new Bio();
Bio b4 = new Bio();
com.omt.temp.Bio bio = new com.omt.temp.Bio();
// Total Objects are created
System.out.println("Total Objects Created By Application :" + ObjectCounter.totalObjectsCreated());
// Get Number Of Objects created for class.
System.out.println("[" + com.omt.temp.Bio.class.getName() + "] Objects Created :"
+ ObjectCounter.getCount(com.omt.temp.Bio.class));
System.out.println("[" + Bio.class.getName() + "] Objects Created :" + ObjectCounter.getCount(Bio.class));
System.out.println("[" + Maths.class.getName() + "] Objects Created :" + ObjectCounter.getCount(Maths.class));
}
}
From this article

Calling variables between different classes through methods

I'm doing an assignment for my computer science class.
I've done quite a bit of the assignment, but I'm having a little bit of trouble pulling the individual variables from the classes. We are just getting into classes and objects and this is our first assignment regarding them so I don't completely understand all of it. So far I've been able to print out the teams, but I haven't been able to pull the individual wins, losses, OTL and OTW so that I can compute whether or not each individual team is a winning team.
What I have done so far is create a class called winningRecord and getPoints, which returns a boolean deciding whether it's a winning team or not. (The formula for a winning team is if the points are > Games Played * 1.5 (as that is an even record).
I don't know how to pull the stats, as it has to be written in the HockeyTeam class. I have set it up so that the constructor sets the variables publicly so that the can be accessed, but as far as accessing them, I'm stumped.
As far as storing them once I am able to access them, would I just make a parallel method that has the points for each team, with just one digit assigned to each bin?
Here is all of the code, thanks for looking.
public class A1Q2fixed {
public static void main(String[] parms) { // main method
processHockeyTeams();
}
/*****************************/
public static void processHockeyTeams() { // processing method
boolean[] winningRecord;
HockeyTeam[] hockeyTeams;
hockeyTeams = createTeams();
printTeams(hockeyTeams);
System.out.print("*********************\n");
printWinningTeams();
winningRecord = HockeyTeam.winningRecord(hockeyTeams);
// printWinningTeams(hockeyTeams);
}
/*********************************/
public static void printTeams(HockeyTeam[] hockeyTeams) {
for (int i = 0; i < hockeyTeams.length; i++) {
System.out.println(hockeyTeams[i]);
}
}
public static void printWinningTeams() {
}
public static HockeyTeam[] createTeams() {
HockeyTeam[] teams;
HockeyTeam team;
int count;
teams = new HockeyTeam[HockeyTeams.getNumberTeams()];
team = HockeyTeams.getTeam();
for (count = 0; (count < teams.length) && (team != null); count++) {
teams[count] = team;
team = HockeyTeams.getTeam();
}
return teams;
}
}
/* hockey team class *******/
class HockeyTeam {
public String name;
public int wins;
public int otw;
public int otl;
public int losses;
public HockeyTeam(String name, int wins, int otw, int otl, int losses) {
this.name = name;
this.wins = wins;
this.otw = otw;
this.otl = otl;
this.losses = losses;
}
public String toString() {
System.out.println(name);
return " W:" + wins + " OTW:" + otw + " OTL:" + otl + " L:" + losses;
}
public static boolean[] winningRecord(HockeyTeam[] hockeyTeam) {
boolean array[] = new boolean[hockeyTeam.length];
String name;
int wins;
int otw;
int otl;
int losses;
for (int i = 0; i < hockeyTeam.length; i++) {
System.out.println(HockeyTeam.name);
}
return array;
}
public static int getPoints() {
int points = 0;
return points;
}
}
/* hockey teams class *******************/
class HockeyTeams {
private static int count = 0;
private static HockeyTeam[] hockeyTeams = {
new HockeyTeam("Canada", 5, 3, 0, 0),
new HockeyTeam("Russia", 5, 1, 1, 2),
new HockeyTeam("Finland", 3, 2, 1, 3),
new HockeyTeam("Sweden", 4, 1, 1, 4),
new HockeyTeam("USA", 1, 2, 2, 3), };
public static int getNumberTeams() {
return hockeyTeams.length;
}
public static HockeyTeam getTeam() {
HockeyTeam hockeyTeam;
hockeyTeam = null;
if (count < hockeyTeams.length) {
hockeyTeam = hockeyTeams[count];
count++;
}
return hockeyTeam;
}
}
Thanks,
Matt.

Sorry but I was only able to understand only a part of your question,from what I understood it seems you are not able to access individual wins, losses, OTL and OTW. I hope this answers your question if not please clarify a bit
To access OTL,OTW have a loop as below:
public class A1Q2fixed
{
public static void main(String[] parms) // main method
{
processHockeyTeams();
}
/*****************************/
public static void processHockeyTeams() // processing method
{
boolean[] winningRecord;
HockeyTeam[] hockeyTeams;
hockeyTeams = createTeams();
printTeams(hockeyTeams);
System.out.print("*********************\n");
printWinningTeams();
winningRecord = HockeyTeam.winningRecord(hockeyTeams);
for(HockeyTeam h:hockeyTeams)
{
System.out.println(h.losses);//To access and print losses
System.out.println(h.otw);//To access and print otw
System.out.println(h.otl);//To access and print otl
}
// printWinningTeams(hockeyTeams);
}
/*********************************/
public static void printTeams(HockeyTeam[] hockeyTeams)
{
for (int i = 0; i < hockeyTeams.length; i++)
{
System.out.println(hockeyTeams[i]);
}
}
public static void printWinningTeams()
{
}
public static HockeyTeam[] createTeams()
{
HockeyTeam[] teams;
HockeyTeam team;
int count;
teams = new HockeyTeam[HockeyTeams.getNumberTeams()];
team = HockeyTeams.getTeam();
for (count=0; (count<teams.length) && (team!=null); count++)
{
teams[count] = team;
team = HockeyTeams.getTeam();
}
return teams;
}
}
Also declare name as Static in HockeyTeam

How to return 2 values from a Java method?

I am trying to return 2 values from a Java method but I get these errors. Here is my code:
// Method code
public static int something(){
int number1 = 1;
int number2 = 2;
return number1, number2;
}
// Main method code
public static void main(String[] args) {
something();
System.out.println(number1 + number2);
}
Error:
Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - missing return statement
at assignment.Main.something(Main.java:86)
at assignment.Main.main(Main.java:53)
Java Result: 1

Instead of returning an array that contains the two values or using a generic Pair class, consider creating a class that represents the result that you want to return, and return an instance of that class. Give the class a meaningful name. The benefits of this approach over using an array are type safety and it will make your program much easier to understand.
Note: A generic Pair class, as proposed in some of the other answers here, also gives you type safety, but doesn't convey what the result represents.
Example (which doesn't use really meaningful names):
final class MyResult {
private final int first;
private final int second;
public MyResult(int first, int second) {
this.first = first;
this.second = second;
}
public int getFirst() {
return first;
}
public int getSecond() {
return second;
}
}
// ...
public static MyResult something() {
int number1 = 1;
int number2 = 2;
return new MyResult(number1, number2);
}
public static void main(String[] args) {
MyResult result = something();
System.out.println(result.getFirst() + result.getSecond());
}

Java does not support multi-value returns. Return an array of values.
// Function code
public static int[] something(){
int number1 = 1;
int number2 = 2;
return new int[] {number1, number2};
}
// Main class code
public static void main(String[] args) {
int result[] = something();
System.out.println(result[0] + result[1]);
}

You could implement a generic Pair if you are sure that you just need to return two values:
public class Pair<U, V> {
/**
* The first element of this <code>Pair</code>
*/
private U first;
/**
* The second element of this <code>Pair</code>
*/
private V second;
/**
* Constructs a new <code>Pair</code> with the given values.
*
* #param first the first element
* #param second the second element
*/
public Pair(U first, V second) {
this.first = first;
this.second = second;
}
//getter for first and second
and then have the method return that Pair:
public Pair<Object, Object> getSomePair();

You can only return one value in Java, so the neatest way is like this:
return new Pair<Integer>(number1, number2);
Here's an updated version of your code:
public class Scratch
{
// Function code
public static Pair<Integer> something() {
int number1 = 1;
int number2 = 2;
return new Pair<Integer>(number1, number2);
}
// Main class code
public static void main(String[] args) {
Pair<Integer> pair = something();
System.out.println(pair.first() + pair.second());
}
}
class Pair<T> {
private final T m_first;
private final T m_second;
public Pair(T first, T second) {
m_first = first;
m_second = second;
}
public T first() {
return m_first;
}
public T second() {
return m_second;
}
}

Here is the really simple and short solution with SimpleEntry:
AbstractMap.Entry<String, Float> myTwoCents=new AbstractMap.SimpleEntry<>("maximum possible performance reached" , 99.9f);
String question=myTwoCents.getKey();
Float answer=myTwoCents.getValue();
Only uses Java built in functions and it comes with the type safty benefit.

Use a Pair/Tuple type object , you don't even need to create one if u depend on Apache commons-lang. Just use the Pair class.

you have to use collections to return more then one return values
in your case you write your code as
public static List something(){
List<Integer> list = new ArrayList<Integer>();
int number1 = 1;
int number2 = 2;
list.add(number1);
list.add(number2);
return list;
}
// Main class code
public static void main(String[] args) {
something();
List<Integer> numList = something();
}

public class Mulretun
{
public String name;;
public String location;
public String[] getExample()
{
String ar[] = new String[2];
ar[0]="siva";
ar[1]="dallas";
return ar; //returning two values at once
}
public static void main(String[] args)
{
Mulretun m=new Mulretun();
String ar[] =m.getExample();
int i;
for(i=0;i<ar.length;i++)
System.out.println("return values are: " + ar[i]);
}
}
o/p:
return values are: siva
return values are: dallas

I'm curious as to why nobody has come up with the more elegant callback solution. So instead of using a return type you use a handler passed into the method as an argument. The example below has the two contrasting approaches. I know which of the two is more elegant to me. :-)
public class DiceExample {
public interface Pair<T1, T2> {
T1 getLeft();
T2 getRight();
}
private Pair<Integer, Integer> rollDiceWithReturnType() {
double dice1 = (Math.random() * 6);
double dice2 = (Math.random() * 6);
return new Pair<Integer, Integer>() {
#Override
public Integer getLeft() {
return (int) Math.ceil(dice1);
}
#Override
public Integer getRight() {
return (int) Math.ceil(dice2);
}
};
}
#FunctionalInterface
public interface ResultHandler {
void handleDice(int ceil, int ceil2);
}
private void rollDiceWithResultHandler(ResultHandler resultHandler) {
double dice1 = (Math.random() * 6);
double dice2 = (Math.random() * 6);
resultHandler.handleDice((int) Math.ceil(dice1), (int) Math.ceil(dice2));
}
public static void main(String[] args) {
DiceExample object = new DiceExample();
Pair<Integer, Integer> result = object.rollDiceWithReturnType();
System.out.println("Dice 1: " + result.getLeft());
System.out.println("Dice 2: " + result.getRight());
object.rollDiceWithResultHandler((dice1, dice2) -> {
System.out.println("Dice 1: " + dice1);
System.out.println("Dice 2: " + dice2);
});
}
}

You don't need to create your own class to return two different values. Just use a HashMap like this:
private HashMap<Toy, GameLevel> getToyAndLevelOfSpatial(Spatial spatial)
{
Toy toyWithSpatial = firstValue;
GameLevel levelToyFound = secondValue;
HashMap<Toy,GameLevel> hm=new HashMap<>();
hm.put(toyWithSpatial, levelToyFound);
return hm;
}
private void findStuff()
{
HashMap<Toy, GameLevel> hm = getToyAndLevelOfSpatial(spatial);
Toy firstValue = hm.keySet().iterator().next();
GameLevel secondValue = hm.get(firstValue);
}
You even have the benefit of type safety.

Return an Array Of Objects
private static Object[] f ()
{
double x =1.0;
int y= 2 ;
return new Object[]{Double.valueOf(x),Integer.valueOf(y)};
}

In my opinion the best is to create a new class which constructor is the function you need, e.g.:
public class pairReturn{
//name your parameters:
public int sth1;
public double sth2;
public pairReturn(int param){
//place the code of your function, e.g.:
sth1=param*5;
sth2=param*10;
}
}
Then simply use the constructor as you would use the function:
pairReturn pR = new pairReturn(15);
and you can use pR.sth1, pR.sth2 as "2 results of the function"

You also can send in mutable objects as parameters, if you use methods to modify them then they will be modified when you return from the function. It won't work on stuff like Float, since it is immutable.
public class HelloWorld{
public static void main(String []args){
HelloWorld world = new HelloWorld();
world.run();
}
private class Dog
{
private String name;
public void setName(String s)
{
name = s;
}
public String getName() { return name;}
public Dog(String name)
{
setName(name);
}
}
public void run()
{
Dog newDog = new Dog("John");
nameThatDog(newDog);
System.out.println(newDog.getName());
}
public void nameThatDog(Dog dog)
{
dog.setName("Rutger");
}
}
The result is:
Rutger

You can create a record (available since Java 14) to return the values with type safety, naming and brevity.
public record MyResult(int number1, int number2) {
}
public static MyResult something() {
int number1 = 1;
int number2 = 2;
return new MyResult(number1, number2);
}
public static void main(String[] args) {
MyResult result = something();
System.out.println(result.number1() + result.number2());
}

First, it would be better if Java had tuples for returning multiple values.
Second, code the simplest possible Pair class, or use an array.
But, if you do need to return a pair, consider what concept it represents (starting with its field names, then class name) - and whether it plays a larger role than you thought, and if it would help your overall design to have an explicit abstraction for it. Maybe it's a code hint...
Please Note: I'm not dogmatically saying it will help, but just to look, to see if it does... or if it does not.