1. Chapter 7 Top-Down Development
Problem-solving approach
Breaking a task down into smaller subtasks
First level of subtasks translates into the main() method
Levels of tasks below main() are developed into a series of additional methods
Refer to page 157 in the text.
© 2007 Lawrenceville Press

2. Used to implement a specific task Methods must be part of a class
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Chapter 7 Using Methods
Used to implement a specific task
Methods must be part of a class
A main() method defines the first level of subtasks with calls to methods that implement the subtasks
Using methods to define tasks is called procedural abstraction
Refer to pages 157 and 158 in the text.
© 2007 Lawrenceville Press

3. method name class method access level return type body
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Chapter 7 A Method
method name
access level
class method
return type
body
public static void fahrenheitToCelsius() { double fTemp, cTemp; Scanner input = new Scanner(System.in); System.out.println("Enter a Fahrenheit temperature: "); fTemp = input.nextDouble(); input.close; cTemp = (double)5/(double)9 * (fTemp - 32); System.out.println("The Celsius temperature is "+cTemp); }
Note: This slide contains animations. Press the space bar or click the mouse button to display each animation.
This slide contains five (5) animations.
Refer to pages 159 and 160 in the text.
A method declaration includes an access level. <press space bar> The keyword public is called an access modifier. A public method can be called by any other method.
The keyword static declares the method a class method. <press space bar> A class method can be called from the class itself.
The return type of a method indicates what type of value the method will send back to the calling statement. <press space bar> The keyword void indicates that nothing is returned.
Method names should indicate an action. <press space bar> Verbs make good method names. A method names should begin with a lowercase letter and then an uppercase letter should begin each word within the name.
The body of the method starts with the first opening brace and ends with the closing brace. <press space bar>
© 2007 Lawrenceville Press

4. Chapter 7 Method Parameters
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Chapter 7 Method Parameters
A method can have parameters for accepting values from a calling statement
Parameters are used inside the method to perform the method's task
The data passed to a method are called arguments
The drawBar() method declaration has one parameter named length: public static void drawBar(int length)
Refer to page 160 in the text.
© 2007 Lawrenceville Press

5. In Java, arguments are passed by value
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Chapter 7 Pass by Value
In Java, arguments are passed by value
A primitive data type gives the method a copy of its value. The method does not have access to the original data.
An object gives the method a copy of its reference that points to methods for changing object data. A method can change the data stored in an object because the method has access to the object's methods.
Note: This slide contains animations. Press the space bar or click the mouse button to display each animation.
This slide contains three (3) animations.
Refer to page 161 in the text.
The object instantiation, String text, associates the object name text with a memory location <press space bar>
The first assignment statement points to the location in memory that stores the mixed-case string <press space bar>
The second assignment statement, moves the pointer to the location in memory that stores the lowercase string <press space bar>
© 2007 Lawrenceville Press

6. Chapter 7 Multiple Parameters
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Chapter 7 Multiple Parameters
A method can have multiple parameters
Multiple parameters must be separated by commas
The order of the arguments passed must match the order of the parameters
The modified drawBar() method declaration has two parameters: public static void drawBar(int length, String mark)
Refer to page 161 in the text.
© 2007 Lawrenceville Press

7. Chapter 7 Method Overloading
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Chapter 7 Method Overloading
More than one method of the same name can be included in a class
The compiler uses the types, order, and number of parameters to determine which method to execute
Refer to page 162 in the text.
The String class is used for representing text. The first character of a string is at index position 0. The last character is at position length()-1.
© 2007 Lawrenceville Press

8. Chapter 7 The return Statement
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Chapter 7 The return Statement
A return statement is used to send a value back to the calling statement
A return statement can return only one value
A method that returns a value must include the return type in the method declaration. For example, the cubeOf() method returns a double: public static double cubeOf(double x)
A method that returns a value is called from a statement that will make use of the returned value. For example: cube = cubeOf(num);
Refer to page 163 in the text.
© 2007 Lawrenceville Press

9. Chapter 7 Documenting Methods
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Chapter 7 Documenting Methods
Methods should be carefully commented so that a reader of the program understands what task the method is performing and what data, if any, will be returned by the method
Method documentation should appear just above a method
Documentation should include a brief description of the method, any preconditions, and the postcondition
Refer to page 164 in the text.
© 2007 Lawrenceville Press

10. Chapter 7 Preconditions and Postconditions
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Chapter 7 Preconditions and Postconditions
The precondition states what must be true at the beginning of a method for the method to work properly.
The postcondition states what must be true after the method has executed if the method has worked properly.
Preconditions and postconditions should not state facts that the compiler will verify. They should also not refer to variables or information outside the method.
The postcondition should not state how the method accomplished its task.
Refer to page 165 in the text.
© 2007 Lawrenceville Press

11. Chapter 7 The GradeConverter Flowchart
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Chapter 7 The GradeConverter Flowchart
Refer to page 166 in the text.
The GradeConverter application begins by
1. prompting the user for a number
2. determining the letter grade that corresponds to the entered numeric grade and displaying the result
3. repeating steps 1 and 2 until the user chooses to quit
© 2007 Lawrenceville Press