class Dog {
    protected String name;
    Dog(String name) {
        this.name = name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return this.name;
    }
}

public void modifyReference(Dog dog) {
    dog.setName("Rex");
}

Dog dog1 = new Dog("Pun");
System.out.println("Before modify: " + dog1.getName());
modifyReference(dog1);
System.out.println("After modify: " + dog1.getName());