object class in java | object in java

Object in Java

Java is a logical entity only.

An entity that has state and behavior is known as an object e.g., chair, bike, marker, pen, table, car, etc. It can be physical or logical (tangible and intangible). The example of an intangible object is the banking system. An object in Java is the physical as well as a logical entity, whereas, a class in

oject in java

An object has three characteristics:

• State: represents the data (value) of an object.

• Behavior: represents the behavior (functionality) of an object such as deposit, withdraw, etc.

    Identity: An object identity is typically implemented via a unique ID. The value of the ID is not visible to the external user. However, it is used internally by the JVM to identify each object uniquely.

object in java

An object is an instance of a class. A class is a template or blueprint from which objects are created. So, an object is the instance(result) of a class.

Object Definitions:

• An object is a real-world entity.
• An object is a runtime entity.
• The object is an entity which has state and behavior.
• The object is an instance of a class.

Example of Object:

object in java exemple

Objects correspond to things found in the real world. For example, a graphics program may have objects such as “circle”, “square”, “menu”. An online shopping system might have objects such as “shopping cart”, “customer”, and “product”.

Declaring Objects (Also called instantiating a class)

When an object of a class is created, the class is said to be instantiated. All the instances share the attributes and the behavior of the class. But the values of those attributes, i.e. the state are unique for each object. A single class may have any number of instances

Example:

object in java example

Initializing an object

The new operator instantiates a class by allocating memory for a new object and returning a reference to that memory. The new operator also invokes the class constructor.

// Class Declaration    public class Dog {     // Instance Variables     String name;     String breed;     int age;     String color;        // Constructor Declaration of Class     public Dog(String name, String breed,                    int age, String color)     {         this.name = name;         this.breed = breed;         this.age = age;         this.color = color;     }        // method 1     public String getName()     {         return name;     }        // method 2     public String getBreed()     {         return breed;     }        // method 3     public int getAge()     {         return age;     }        // method 4     public String getColor()     {         return color;     }        @Override     public String toString()     {         return("Hi my name is "+ this.getName()+                ".\nMy breed,age and color are " +                this.getBreed()+"," + this.getAge()+                ","+ this.getColor());     }        public static void main(String[] args)     {         Dog tuffy = new Dog("tuffy","papillon", 5, "white");         System.out.println(tuffy.toString());     } }

Output:

Hi my name is tuffy.

My breed,age and color are papillon,5,white