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Inside Class Methods

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Chapter 4. Inside Class Methods. What are variables?. Variables store values within methods and may change value as the method processes data. Variables. The scope of a variable determines how long it holds its value.

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Presentation Transcript
what are variables
What are variables?
  • Variables store values within methods and may change value as the method processes data.
variables
Variables
  • The scope of a variable determines how long it holds its value.
    • Local variables maintain their scope within the block of code in which they are declared.
    • Local variables are not fields of the class.
declaring and initializing variables
Declaring and Initializing Variables
  • Declare a variable by identifying its type and the identifier (name):
    • double averageSpeed;
  • Initialization is when you declare a variable and assign it a value at the same time:
    • double averageSpeed = 21.6;
what are operators
What are operators?
  • Operators are symbols that take action within a program.
    • Assignment operator (=) assigns a value to a field or variable:
      • averageSpeed = 21.6;
    • Mathematical operators include:
      • +, -, *, and /
    • Relational operators include:
      • <, >, ==, and !=
a self assignment operator
A Self-Assignment Operator
  • Manipulates a variable and assigns the results back to itself.
    • Self-assignment operators include +=, -=, *=, and %=
    • int x = 5;
    • int y = 6;
    • x += y;
    • x has the value (5 + 6) = 11
precedence
Precedence
  • Java follows mathematical rules of precedence.
    • Multiplication and division are handled first, followed by addition and subtraction
    • Use parentheses to force evaluation
increment and decrement operators
Increment and Decrement Operators
  • The increment operator (++) means increment (add) by one.
    • ++x;
  • The decrement operator (--) means decrement (subtract) by one.
    • --x;
prefix vs postfix
Prefix vs. Postfix
  • Prefix notation increments, then fetches:
    • int x = 5;
    • int y = ++x;
    • Value of y is 6 (1 + 5), value of x is 6
  • Postfix notation fetches, then increments:
    • int x = 5;
    • int y = x++;
    • Value of y is 5, value of x is 6
what is a constant
What is a constant?
  • A constant is a variable with a fixed value (cannot be changed).
    • Use the keyword final to designate a constant.
    • Constant identifiers are typically UPPER_CASE notation to distinguish them from other variables.
relational operators
Relational Operators
  • Evaluate the equality or inequality of two intrinsic types.
    • Return a boolean value (true or false)
    • Equality: ==
    • Inequality: <, >, <=, >=, != (not equal)
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