Objects and Data types in Java

Object:

• An Object is a physical entity meaning that it will physically create a heap memory at runtime.
• An object is a combination of state (data/variables-Color, RAM) and behavior(methods /functions-Call, SMS).

Syntax:

Classname referenceName = new Classname();

• new is a Java keyword.
• If we mention a new keyword in object,JVM will allcated one memory in heap at runtime.

Data Types:

• Data types specify what type of data a variable can store.
• Java has two main types of data types:
  • Primitive data types.
  • Non-primitive data types.

Primitive data type:
-Primitive data types store simple values.
-Memory management of primitive data type is stack.
-There are 8 primitive data types in java.
1.short
2.byte
3.int
4.long
5.float
6.double
7.char
8.boolean
-These 8 primitive data types are known as Keywords.

Non-Primitive Data Type:

-String is a Non-primitive data type.

Size and Range of data types:

Size of all primitive data types:
1.short = 2 byte.
2.byte = 1 byte.
3.int = 4 byte.
4.long = 8 byte.
5.float = 4 byte.
6.double = 8 byte.
7.char = 2 byte.
8.boolean = 1 bit.

To calulate range:

   -1 byte = 8 bit = 2*2*2*2*2*2*2*2.
                   = 256 (so 256/2=128)
   - To store the negative value the range starts from -128 to 127(The range ends at 127 because 0 i included).

Range:

 -short = -32,768 to +32,767.
 -byte = -128 to 127.