Unit 1 Primitive Types

  • String literal - an exact sequence of characters enclosed between two quotation marks
  • Different Errors
    • Syntax/compiler error: program won't compile due to typos
    • Exception
    • Logic error: actual output differs from anticipated output

Data Types

  • Determine what type of value is stored ### Variables
  • variable: name for memory location holding a certain type of value
    • no spaces
    • can't start with #
    • no special characters (anything besides letters/digits)
    • no Java reserved keywords
    • use camelCase conventions #### Declaring
    • assignment operator (=) is used to initialize variable or change its associated value ### Primitive
  • Examples:
    • boolean (1 bit)
    • int (32 bits)
      • if the integer result of an expression is beyond the range there will be an overflow error
    • double (64 bits) ### Reference

Arthmetic Operators

  • INCLUDES: +, -, *, /, %
  • operations with only int ==> output int
  • operations with only double ==> output double
  • operations with both int and double ==> * output double
  • division by zero ==> ArithmeticException

Compound Assignment Operators and Incrememt/Decrement Operators

  • +=, -=, *=, /=, %=
  • Using these will change the value of the variable to the result of the operation
  • Increment/Decrement:
    • ++: adds 1
    • --: subtracts 1

Unit 2 Using Objects

Constructors

  • Used to initialize attributes for an object
// Syntax example

public Turtle{
    public Turtle(String nm, int ag, boolean it){ // signature with formal parameters
        name = nm;
        age = ag;
        isTortoise = it;
    }
}

// call by value: pass actual parameters to constructor
Turtle Shellbert = new Turtle("Shellbert", 4, true); // creating an object with "new" keyword calls constructor

Vocab

  • signature: constructor name and parameter list

  • parameter list: lists type of values passed and their variable names (formal parameters)

    • parameter: value passed into a constructor (actual parameters), must match types specified in parameter list
    • call by value: initializes formal parameters with copies of the actual parameters

  • overloaded constructors: there are multiple constructors with same name, differing signatures

  • no argument constructor: constructor with no parameters, sets attributes (instance variables) of object to default values

    • String: null
    • boolean: false
  • null: variable reference doesn't actually contain an object