Java Data Types

1. Primitive Data Types:

• byte: 8-bit signed integer.

  byte myByte = 127;

• short: 16-bit signed integer.

  short myShort = 32767;

• int: 32-bit signed integer.

  int myInt = 2147483647;

• long: 64-bit signed integer.

  long myLong = 9223372036854775807L;

• float: 32-bit floating-point (decimal) number.

  float myFloat = 3.14f;

• double: 64-bit floating-point (decimal) number.

  double myDouble = 3.141592653589793;

• char: 16-bit Unicode character.

  char myChar = 'A';

• boolean: Represents true or false values.

  boolean myBoolean = true;

2. Reference Data Types:

• String: Represents a sequence of characters.

  String myString = "Hello, World!";

• Arrays: Ordered collections of elements of the same type.

  int[] numbers = {1, 2, 3, 4, 5};

• Classes and Objects: Instances of user-defined classes.

  class Person {
      String name;
      int age;
  }
  
  Person person1 = new Person();
  person1.name = "Alice";
  person1.age = 25;

• Interfaces, Enums, etc.: Other user-defined types.

Primitive vs. Reference:

• Primitive types are value types: They store the actual value.
• Reference types are reference types: They store a reference (memory address) to the actual data.

Default Values:

• Primitive types: Have default values (e.g., 0 for numeric types, false for boolean).
• Reference types: Default to null (indicating no reference to an object).

Wrapper Classes:

Java provides wrapper classes for each primitive data type, which allow primitive types to be used as objects. These classes are part of the java.lang package:

• Byte, Short, Integer, Long, Float, Double: Wrapper classes for numeric types.
• Character: Wrapper class for char.
• Boolean: Wrapper class for boolean.

Wrapper classes are often used in situations where objects are required, such as in collections or when working with Java generics.