Usually in a POJO you have what are called a getter and a setter method for every variable of the object. In your case:
public class HillClimber{
private int ballWeight;
public HillClimber(){
this.ballWeight = 200;
}
public void setBallWeight(int ballWeight){
this.ballWeight = ballWeight;
}
public int getBallWeight(){
return this.ballWeight;
}
}
In this way you can access the variable ballWeight via get and set method. You don't access it directly like in hc.ballWeight, which is possible but is a bad practice, and prevent this access type declaring your variable as private (meaning that only the class in which it is declared can directly access it).
To fullfill your request of adding one at every run of the game you can therefore call
hc.setBallWeight(++hc.getBallWeight()); //Equivalent to hc.setBallWeight(hc.getBallWeight() + 1);
I usually don't use this approach if the class isn't automatically generated (as in an Hibernate context), but instead declare another method in the HillClimber class
public void incrementBallWeight(int ballWeightToAdd){
this.ballWeight += ballweiGhtToAdd; //Equivalent to this.ballWeight = this.ballWeight + ballweiGhtToAdd;
}
or if I always need to add only one to my variable
public void incrementBallWeight(){
this.ballWeight++;
}
and then simply call incrementBallWeight after every game run.
NB: to have this working you will have to use always the same instance of HillClimber. In your main
public class Game{
private HillClimber hc = new HillClimber(); //Create the instance and sets ballWeight to 200
public static void main(String[] args){
playGame();
hc.incrementBallWeight(); //ballWeight == 201
playAnotherGame()
hc.incrementBallWeight(); //ballWeight == 202 -> Always the same instance of HillClimber (hc)
.
.
.
}
}
EDIT
I think your problem is greater than that. You are asking to save the state of a variable ( meaning that this value should be available also if you turn off and on your pc) without using a permanent storage. This is simply unachievable.
You should rethink your program (and I mean java program, not a "game run") to not stop after every game run. You can do this in different ways: via Swing GUI, via user input from stdin and so on. If you want some help on this topic, we need to know more of your code (maybe putting the whole of it is best).
OR you can use a file to store your value, which is not as difficult as you think. (Also).
