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GeneralProgramming

Types of comments

  • Single Line Comment
  • Block Line Comment
  • Javadoc comment :
    • Javadoc comments behaves same as above comments, but it can be used generate documentation

Datatypes

Primtive Dataype

  • Integer Type

    • byte - bits = 8
    • short - bits = 16
    • Int - bits = 32
    • long - bits =64

  • Floating Point Type

    • float - bits = 32
    • double - bits =64

  • Character Type

    • Stores single unicode character

  • Boolean Type

    • True or False

Operator Precedence

  • Postfix (X++ X--) > Prefix (++X --X) > Multiplicative (* / %) > Additive ( + -)
  • We can override the precedence with the parenthesis

Type conversion

  • Implicit Type Conversion
    • This type of conversion is automatically done by the compiler
    • Mixed integer sizes
      • Uses the largest integer in the equation
    • Mixed floating point sizes
      • Uses double
    • Mixed floating point and Integer
      • Uses largest floating point
  • Explicit Type Conversion
    • Need to use cast operator for this

Conditional Logical Operator and Logical Operator

  • Logical Operators

    • AND (&)
    • OR (|)
    • XOR (^)
    • NOT (!)

  • Conditional Logical Operator

    • AND (&&) - exectues right only when left is true
    • OR (||) - executes right only when left is false

Parameter Passing

  • Parameters passed "by value"
    • Parameter receives a copy of the original value
  • Parameters passed "by reference"
  • Parameters are passed positionally

Main methods runs as the Program Entry point and command line arguments are passed to it

Strings

  • Strings are immutable

    • String variable do not directly hold their value, instead it holds a reference to the instance of string
    • Change in the value creates as new instance of the string

  • String equality

    • '==' when applied to strings then it checks whether these variable points to same reference. So it does not compare content of the strings but reference
    • We use equals method to compare content of Strings

  • Interning a String

    • This methods makes several string variables to point to same string reference

  • String Builder

    • Provides mutable string buffer
      • Efficiently constructs string values
    • We use toString() to extract values from the string builder

Other Data Types

  • Time & Data
    • Instant class
    • LocalDate
    • DateTimeFormatter

Primitive wrapper class

  • Each primitive types has a wrapper
  • Wrapper classes has several methods
    • Coverting to from other types
    • Extracting values from strings
    • Finding min/max values