Inside Class Methods

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# Inside Class Methods - PowerPoint PPT Presentation

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
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.
• 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
• 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?
• 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
• 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
• 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
• The increment operator (++) means increment (add) by one.
• ++x;
• The decrement operator (--) means decrement (subtract) by one.
• --x;
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?
• 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
• Evaluate the equality or inequality of two intrinsic types.
• Return a boolean value (true or false)
• Equality: ==
• Inequality: <, >, <=, >=, != (not equal)