Writing Methods in Programming

• Writing methods is about creating named blocks of code

What is a Method?

• A method is a named block of code that is executed when is called by its name.
• The code runs top to bottom
• The code runs until it returns a value or reaches the end of the code block.
• Methods are like miniature programs, they take in data as parameters, perform a function, and return a value.
• Methods contains the code that runs when called by name, and executes all the code within its code block.
• A code block consists of everything between the method's curly brackets.
• Methods can contain other code blocks, such as if statements and "for" loops.
• All code inside curly brackets directly under the method declaration forms the method.

Why Use Methods?

• Methods are convenient as they can be called repeatedly without rewriting the code.
• Methods prevent the need to rewrite "for" loops for similar calculations each time.

Basic Syntax

• public static void main(String[] args) is the basic syntax:
  • public and static are access modifiers.
  • void specifies the return type.
  • main is the method name
  • String[] args represents the method's parameters.
• Running a program in a block of code is running a method.
• Right-clicking a class and running void main(String[] args) executes that method which contains all of the code.
• public void main(String[] args) is a special method in Java.
• When a method is called, the main program execution jumps to that method, completes its task, and then returns to the main program.

Parts of Method: Header

• public static boolean isPositive(int num) is the method's header.
• The header declares a method and includes the return type, name, and parameters.
• The method's signature consists of the name and parameter list

Parts of Method: Access Modifier

• public and static are access modifiers

Parts of Method: Return Type

• boolean is the return type
• Once finished, the method return a boolean value to where it was called.
• Return type indicates the type of value or an answer gets sent back.

Parts of Method: Name/Identifier

• isPositive is the name of the method
• Methods should follow variable naming conventions, such as being descriptive and using camelCase, starting with a lowercase letter.
• Methods are called using parentheses, differentiating them from variables

Parts of Method: Parameter List

• int num is the method's parameter list
• Methods can have multiple parameters or none.
• Parameters are placeholders for values passed in by the caller.
• The parameter list specifies what information a method needs from the main program to execute.

Parts of Method: Body

• The method's body is the block of code between curly brackets, which runs when the method is called.
• Methods must return a value of the specified type before the closing curly bracket (unless the return type is void).

The Return Keyword

• The return keyword indicates that a method's job is done and it is immediately returning a value.
• Methods must return the data type specified in the method header.
• Any code after a return is unreachable because the method has already returned to where it as called.

isPositive(int num) Method

• If the num parameter is greater than 0, the isPositive(int num) method needs to return a value of true.
• If the condition num > 0 isn't met, the method won't return anything without fixing this.
• To ensure the isPositive(int num) method always returns a value, an else statement can be used to return false when num is not greater than 0.
• Simplified versions of the isPositive() method achieve the same result. return num > 0;
• The isPositive() method can be used in a main program and called when needed.

More on the Return Keyword

• When the return keyword is encountered, the method stops executing and returns a value.
• Code after a return statement is unreachable.
• If a return statement is inside an if statement or a loop, there is a chance the statement won’t run. There must be a return statement in an else statement.
• When a method returns a value, its job is done.
• Code that cannot be executed is called unreachable code

The Void Return Type

• A void return type means a method does not return a value.
• Methods with a void return type still run its code block, but do not return a value.
• Void methods can still return, but will not return a value.
• Void return type methods are the only methods where a return isn't explicitly required.
• If a method returns a `boolean, a boolean must be returned.
• When a method returns void, it could return, but the compiler won’t complain if it returns at the end.

Calling Methods/Parameter Matching

• avgOf2()method call needs to use the method name.
• The avgOf2 method requires 2 parameters, so data needs to be sent over for it to complete its job.
• The avgOf2 method is designed to return a double, so the returned value must be stored to continue

Where to Write Methods

• Methods must be written outside of other methods, but inside a class.

Benefits of Writing Methods

• Methods allows for easier debugging since, any issues can be located quickly.
• Methods result in less code repetition, and called with new parameters.
• Methods are easier to read.