Lecture 02 Object Oriented Programming

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Lecture 05Method
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Outlines

• Method
• Creating method
• Method call
• Passing parameters
• Method overloading
• Math class

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Methods

• A method is a series of statement that carry out
  some task.
• Java API provides a rich collection of classes
  and methods
• User-defined method
• Build-in method
• Math class method

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Method

• A method must include the following
• A declaration (or header)
• An opening curly bracket
• A body
• A closing curly bracket
• The method declaration contains the following
• Optional access modifiers
• The return type for the method
• The method name
• An opening parenthesis
• An optional list of method argument
• A closing parenthesis

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Creating Method

• Structure
• modifier returnValueType methodName (list of
  parameters)

Method header
public static int max (int num1, int
num2) ..
Method body
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Return Type

• Void
• does not return a value to the calling program
• Nonvoid
• returns a single value to the calling program.

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Method Name

• A verb or a verb phrase.
• Capitalize the first letter of the second word
• Never mention the method name inside of the
  function definition except if the function is
  recursive.

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Parameter Listings

• Are variables sent to the method to perform its
  designated tasks.
• Must determine and list the data type of each
  parameter before listing its name.

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Method Body

• Includes the statements that will perform the
  task
• Must be framed with curly braces.
• Start by defining variables (only the ones
  outside of the class and not listed within the
  parameter listing)

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Calling a Method

• A method is invoked by a method call
• Specifies the method name and provides
  information (argument)
• Two ways to call a method
• Based on whether the method returns a value or
  not
• Return value
• int larger max (3,4)
• System.out.println( max (3,4))
• Return void
• A call to the method must be a statement
• System.out.println ( Welcome)
• Use the method name as a statement

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Example

• Max

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Passing Parameters

• Pass by value
• When you invoke a method with parameters, a copy
  of the value of the actual parameter is passed to
  the method
• Example Swap
• Formal parameters are changed in the example, but
  the actual parameter are not affected

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Overloading Methods

• Create another method with the same name, but
  different parameters
• Example
• Overloading the Max method

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Commonly Used Math Class Methods
Method
Description
abs (x)
Absolute value of x
exp (x)
Exponential method ex
log (x)
Natural logarithm of x (base e)
max (x, y)
Larger value of x and y
min (x, y)
Smaller value of x and y
pow (x, y)
X raised to power y (xy)
sqrt (x)
Square root of x
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Example

• Car Loan Systems
• Shipping Charge