# Methods

## What are methods

A java method can be interpreted as a subprogram. It is a collection of statements taht are grouped togehter to perform an operation

## Built- in vs User-defined Methods

Built-in:
BUild-i nmethods arep art of hte complier package such as system.out.println

Function (return) - Type: it calcualtes and return a value
```java
public static int claculate(int number){
```

procedure-type: executes some commands

Function (return)- type: 
pubic static return type method name (parameter 1)

procedure-type method:
public static void method-name (paramenter 1)

## How to create a method

In general, method declarations has 5 basic components (figure 2.):
- **Modifier:** defines access type of the method i.e. from were it can be accessed in your application (For example: public)
- **The return type:** the data type of the value returned by the method or void if it does not return a value (procedure and function type)
- **Method name:** a specific names that identifies the method that  can be used to invoke it later
- **Parameter list:** Comma separated list of the input parameter are defined preceded with their data type, within the enclosed parentheses, If there are no parameters, you must use empty parenteses()

## Method declaration
- **Method body:** It is enclosed between braces. the code that you need to be execute to perfrom your intended operations

```java
public int max(int x, int y) {

```

## How to call a method (method invocation

To invoke a method you need the method name with the parameter list defined between parentheses

Exammple:
Method Name (paramter list)

Must have () parentheses when calling a method, even with no passing parameters

## Pass-By-Value
**What happens:** When a method is called ,a copy of the value of each argument is passed  to the method

**In the second method:** This copy can be changed inside the method, however such a change has no effect on the actual argumnet

```
int num=10;
double decimal = 5.2;
NumberManeuvers(num decimal);
System.out.println("num = " + num + "and decimal = " + decimal);

public static void numberManeuvers(int i, double j) {
    if(i == 10) {
        j = 6.2;
        i = 12;
    }
}
// output = num = 10 and decimal = 5.2
```

## Pass-By-Reference