Methods Flashcards
methods, char variables, and boolean
Write the General Structure of a Method
public static returntype methodname (zero or more input variables){
* // create local variables
* // do math ao logic
* // return result based on returntype (if applicable)
}
Function of “methodname” in General Structure
public static returntype methodname (zero or more input variables){
* // create local variables
* // do math ao logic
* // return result based on returntype (if applicable)
}
give a name to method
* use this name in main program to ‘call’ the method
Function of “zero or more input variables” in General Structure
public static returntype methodname (zero or more input variables){
* // create local variables
* // do math ao logic
* // return result based on returntype (if applicable)
}
take data in through input variables
- Note: variable names in main program do not have to match names in method
- Note: if there are no input values, leave ( ) blank when calling method.
- Note: the input variables do not have to match the returntype/output
Function of “returntype” in General Structure
public static returntype methodname (zero or more input variables){
* // create local variables
* // do math ao logic
* // return result based on returntype (if applicable)
}
specifies type of data being output by the method
Examples of ReturnTypes…
String
int
double
boolean
void (a.k.a. nothing)
long
char
Explain Boolean
a variable type which holds the values: true or false
- has no quotations
What word is “char” short for?
character
Special features of Char variables
can use math comparison symbols on them
Function of:
strWord.charAt(integer#)
take the single character with the index/subscript of the number in () from a given string
Write the line of code which takes a single letter in a string USING CHAR VARIABLES.
chrLetter = strWord.charAt(integer#);
Type of quotations used by char variables
single quotations
Type of quotations used by String variables
double quotations
Function of return keyword
returns a value back to main program
Which return type does not need a return keyword?
return type: void
Do local variables in methods exist in the main method?
No
Write code to call a method in a different file (eg. allisontools file)
allisontools.methodname(input variables);
Benefits of Methods
- main programs are shorter
- more efficient – you do not need to rewrite the same lines of code (math/logic) over and over again
- reduces the number of errors – you can write parts of the program at a time and test as you go
- easier collaboration/teamwork – different team members can work on different methods
- money: tool files can be so useful that you can sell them for a price
Methods
pieces of code which programmers can access over and over again when its functionality is needed
When do methods run?
when placed in main method & given proper input
Alternate Names for Methods
Methods
Functions
Procedures
Long Variable Type
integers that can hold numbers larger than 2 billion
integer variable data that can hold numbers larger than 2 billion
Function of Long Variables
Why use int when you have long?
to save RAM
Where must tools files be located
in same folder as the programs which use it
Implement a method double sphereVolume(double r) that calculates and returns the volume of a sphere given its radius r. Use the formula: V = (4/3) × π × r³. Test this method in a program.
Write a method boolean isLeapYear(int year) that returns true if the given year is a leap year, otherwise false. Use the formula: A year is a leap year if it is divisible by 4 but not divisible by 100, unless it is also divisible by 400. Test this method in a program.
Create a method int charFrequency(String text, char c) that counts and returns the number of times a character c appears in the given string text. Write a program to test this method.
Define a method int countVowels(String word) that counts and returns the number of vowels (a, e, i, o, u) in the given string. Write a program to test this method.
USING CHAR
