VARIABLES AND DATA TYPES

• JAVA KEYWORDS


  These are reserved keywords that cannot be used as variables, methods, classes, or any other identifiers.
• JAVA KEYWORDS

  Take note: true, false, and null are not keywords, but they are literal and reserved words that cannot be used as identifiers.
• JAVA VARIABLES


  containers for storing data values. These are data containers that save the data values during Java program execution.
• Different Types of Variables

  • String
  • int
  • float
  • char
  • Boolean
• String 


  stores text, such as "Hello". String values are surrounded by double quotes
• int 


  stores integers (whole numbers), without decimals, such as 123 or -123
• float 


  stores floating point numbers, with decimals, such as 19.99 or -19.99
• char 


  stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes
• Boolean 


  stores values with two states: true or false
• To Declare (Create) Variables

  Syntax:

  Type variableName = value;
• "final" or "constant"


  which means unchangeable and read-only:
• To Declare (Create) Variables

  Declaring more than one variable of the same type, you can use a comma-separated list

  Syntax:

  int num1, num2, num3;
• JAVA VARIABLES


  Data types specify the different sizes and values that can be stored in the variable.
• There are two types of data types in Java:

  Primitive data types

  Non-primitive data types
• Primitive data types: 


  Include boolean, char, byte, short, int, long, float, and double.
• Non-primitive data types: 


  Include Classes, Interfaces, and Arrays.
• Integral Data Types

  store whole numbers, positive or negative (such as 123 or -456), without decimals. Valid types are byte, short, int, and long.
• Boolean Types


  is a primitive data type used to represent a logical value.
• Character Types


  used to store a single character.
• String Types


  used to represent a sequence of characters.