[Java] Object and Class

  Object and Class

- Object is the physical as well as logical entity

- Class is the logical entity only

1. Object in java

- An entity that has state and behavior is known as an object

- An object has three characteristics

1_1. state: represents data(value) of an object

1_2. behavior : represents the behavior(functionality) of an object such as deposit, withdraw

1_3. identity : Object identity is typically implemented via a unique ID. The value of the ID is not visible to the external user. But is is used internally by the JVM to identify each object uniquely

- Object is an instance of a class

: Class is a template or blueprint from which objects are created

2. Class in Java

- A class is a group of objects that has common properties. It is a template or blueprint from which objects are created

- A class in java can contain

• data member
• method
• constructor
• block
• class and interface

2_1. new Keyword

- The new keyword is used to allocate memory at runtime

3. Example

- Object gets the memory in Heap area and reference variable refers to the object allocated in the Heap memory area