如果两个对象访问同一个实例变量会发生什么？

Question

i have created an user defined object which accesses an instance variable and a method.Then i created an array of of 3 elements in which one reference variable has a reference to object that i initially created.now what happens to instance variable of class if both references refer to same object.why its null says ruff??

CODE:
public class Dog{
String name;
public static void main(String[] args){

Dog dog1=new Dog();
dog1.bark();
dog1.name="Brat";


Dog myDogs[]=new Dog[3];
myDogs[0]=new Dog();
myDogs[1]=new Dog();
myDogs[2]=dog1;


myDogs[0].name="Fred";
myDogs[1].name="Marge";

System.out.print("last dogs name is ");
System.out.println(myDogs[2].name);

int x=0;
while(x< myDogs.length){
myDogs[x].bark();
x=x+1;
}



}

public void bark(){
System.out.println(name+" says Ruff");
}


}

OUTPUT:

null says Ruff
last dogs name is brat
Fred says Ruff
Marge says Ruff
brat says Ruff

Answer 1

Because you are calling dog1.bark() before setting dog1.name , so name is null when calling dog1.bark() . That's why dog1.bark() prints null for name

Dog dog1=new Dog();
dog1.bark();
dog1.name="Brat";

If you set dog1.name before like this

Dog dog1=new Dog();
dog1.name="Brat";
dog1.bark();

Then it will print Brat says Ruff

Answer 2

Issue is you are calling the method dog1.bark() before setting a value for the class property String name,so if you don't initialize a value for a class property before the creation of the object java will automatically assign a default value.So Object references like String name will be initialized with null .So that's why you are getting the output as null for the name.

So in the second code snippet what you are doing is you are assigning "Brat" right after the object creation then you are calling the dog1.bark(),so in this situation your logic inside the bark() function will change the String name = null -----> default value to name = "Brat" ,that's why you are getting an output of "Brat says Ruff"