I always use constuctor only for attributes of one object. But i thin when i wrote this :
public Predmet(int esp,int obaveze,int cena){
this.cena=cena;
this.obaveze=obaveze;
this.esp=esp;
List j = new ArrayList();
j.add(8);
this.nesto=(int) j.get(0);
}
where are stored this ArrayList,does it part of object,or is on stack and have reference to array in heap?
The ArrayList is created on the heap and only referenced by the local variable j from the stack here. After the execution of the constructor it will be eligible for garbage collection.
Constructor is working very similar the way methods work. At runtime, anything you define inside constructor/method are called local variables. Their scope will end as soon as execution hits the end of the constructor/method. After consturctor, your list will be eligible for GC. However, this.nesto will still get value 8 as its primitive type.
First, please don't use single variable names! This is bad practice and makes files harder to read. Using a more descriptive name helps to promote code readability.
The way that List j is created, it only exists in the scope of the constructor. After your constructor, List j is no longer accessible. If you wanted it to be accessible after the constructor, have a field for the object. For example:
public class Example {
private int specialNumber;
private List<Integer> numberList;
/**
* Constructs a new Example Object
*/
public Example(int exampleNum){
// specialNumber can be accessed from a Getter method (getSpecialNumber)
this.specialNumber = exampleNum;
this.numberList = new ArrayList<Integer>();
this.numberList.add(exampleNum);
// numberList is a field of this Example now
List<Integer> disappearingList = new ArrayList<Integer>();
disappearingList.add(exampleNum);
// After this method finishes, disappearingList will be gone
}
// disappearingList is no longer accessible
/**
* Gets this Example's specialNumber value
* @return int this.specialNumber
*/
public int getSpecialNumber(){
return this.specialNumber;
}
/**
* Gets this Example's numberList
* @return List<Integer> this.numberList
*/
public List<Integer> getNumberList(){
return this.numberList;
}
}
There is probably a way to hook into some of the Java cleaning methods and pull it out, but that will get a little messy. If you want to be able to create an Object inside another Object, and use it after the constructor, it must be saved as a field.
