Object References and Their Mechanisms
Definition
Object references
Variables that store the memory address of an object rather than the object itself.
Object references are like pointers in languages such as C++ or Golang, where variables can hold the address of primitive value or an object in memory.
Example- In Java, when you create an object using the new keyword, the variable holds a reference to the object:
Student student1 = new Student("Alice", 16);- Here, student1 is a reference to the Student object.
Sharing References and Modifying Objects
When you assign one object reference to another, both references point to the same object.
Examplepublic class Student{
public String name;
public int age;
public Student(String nameIn, int ageIn){
this.name = nameIn;
this.age = ageIn;
}
public static void main(String[] args){
Student student1 = new Student("Alice", 13); // initialise object
System.out.println("student1 initial name: " + student1.name + ", age: " + student1.age);
Student student2 = student1; // share reference
System.out.println("student2 initial name: " + student2.name + ", age: " + student2.age);
}
}
Changes made through one reference affect the object and are visible through other references.
Examplepublic class Student{
public String name;
public int age;
public Student(String nameIn, int ageIn){
this.name = nameIn;
this.age = ageIn;
}
public static void main(String[] args){
Student student1 = new Student("Alice", 13); // initialise object
System.out.println("student1 initial name: " + student1.name + ", age: " + student1.age);
Student student2 = student1; // share reference
System.out.println("student2 initial name: " + student2.name + ", age: " + student2.age);
// change student2 attributes
student2.age = 16;
student2.name = "Bob";
System.out.println("student2 new name: " + student2.name + ", age: " + student2.age);
System.out.println("student1 new name: " + student1.name + ", age: " + student1.age);
}
}
Null References
A reference that does not point to any object is called a null reference.
ExampleStudent student3 = null;Accessing methods or properties on a null reference will result in a runtime error (e.g., NullPointerException in Java).
