Inside Class Methods

Chapter 4

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What are variables?Variables store values within methods and may change value as the method processes data.

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VariablesThe 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.

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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;

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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 !=

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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

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PrecedenceJava follows mathematical rules of precedence.

Multiplication and division are handled first, followed by addition and subtraction

Use parentheses to force evaluation

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Increment and Decrement Operators

The increment operator (++) means increment (add) by one.

++x;

The decrement operator (--) means decrement (subtract) by one.

--x;

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Prefix vs. PostfixPrefix 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

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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.

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Relational OperatorsEvaluate the equality or inequality of two intrinsic types.

Return a boolean value (true or false)

Equality: ==

Inequality: <, >, <=, >=, != (not equal)