CP-WEEK10

Java Programming: Data Types and Variables

1. Understanding Data Types

  • Importance: Data types are fundamental in Java programming as they define the size and type of data that can be stored in a variable.

  • Types of Data Types:

    • Primitive Data Types: These include basic types with pre-defined values.

    • Non-Primitive Data Types: Refer to objects created by the programmer, including classes, interfaces, and arrays.

2. The Eight Primitive Data Types in Java

  • byte: 1 byte, stores values from -128 to 127.

    • Example: byte myNum = 100;

  • short: 2 bytes, stores values from -32,768 to 32,767.

    • Example: short dollar = 5000;

  • int: 4 bytes, stores values from -2,147,483,648 to 2,147,483,647.

    • Example: int myNum = 1000000;

  • long: 8 bytes, stores larger whole numbers; suffix with 'L'.

    • Example: long myNum = 15000000000L;

  • float: 4 bytes, stores fractional numbers (6-7 decimal digits); suffix with 'f'.

    • Example: float total = 5.75f;

  • double: 8 bytes, stores larger fractional numbers (15 decimal digits); suffix with 'd'.

    • Example: double value = 555.7523d;

  • char: 2 bytes, stores a single character in single quotes.

    • Example: char myGrade = 'F';

  • boolean: 1 bit, stores true or false values.

    • Example: boolean isJavaFun = true;

3. Variable Declaration and Initialization

  • Declaration: Define the data type and variable name.

    • Example: int a;

  • Initialization: Assign a valid value to a variable.

    • Example: a = 5; or int b = 10;

  • Combining Declaration and Initialization: You can declare and initialize simultaneously.

    • Example: double pi = 3.14;

4. Types of Variables in Java

  1. Local Variables: Declared within a method, only accessible within that method.

  2. Instance Variables: Declared outside methods, using the keyword static determines their behavior.

  3. Static Variables: Initialized once, at the start of program execution.

5. Working with Expressions

  • Expressions: Combinations of operators, literals, or constants, and variables returning a specific data type.

    • Example: weight_lbs = 2.2 * weight_kg;

6. Java Operators

Types of Operators

  1. Arithmetic Operators: Perform math operations.

    • Examples: +, -, *, /, % (modulo)

  2. Assignment Operators: Assign values to variables.

    • Examples: =, +=, -=, *=, /=, %=, etc.

  3. Relational Operators: Compare values, returning boolean.

    • Examples: <, >, <=, >=, ==, !=

  4. Logical Operators: Evaluate logical expressions (true/false).

    • Examples: && (AND), || (OR), ! (NOT)

  5. Unary Operators: Operate on a single operand.

    • Examples: ++ (increment), -- (decrement), - (negative sign)

7. Summary of Key Concepts

  • The eight primitive data types in Java: byte, short, int, long, float, double, char, and boolean.

  • A variable serves as a named memory location to store values.

  • Expressions consist of operands and operators, with operator precedence affecting the evaluation order.

  • Operators, including arithmetic, assignment, relational, logical, and unary types, perform various functions in Java.