[Excellent Tutorial] Java Method (1)

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We often use System.out.println(), so what is it?

println() is a method (Method), and System is the system class (Class), and out is the standard output object (Object). The usage of this sentence is to call the method println() in the standard output object out in the system class System.

So what is the method?

Java methods are a collection of statements that together perform a function.

1) A method is an ordered combination of steps to solve a type of problem

2) A method is contained in a class or object

3) A method is created in a program, Referenced elsewhere

Definition of method

Generally, defining a method contains the following syntax:

Modifier return value type method name (Parameter type parameter name) {

...

Method body

...

return return value;}

The method contains a method header and a method body. The following are all parts of a method:

1) Modifiers: Modifiers, which are optional, tell the compiler how to call the method. Defines the access type for this method.

2) Return value type: Methods may return values. returnValueType is the data type of the method return value. Some methods perform the required operation but do not return a value. In this case, returnValueType is the keyword void.

3) Method name: It is the actual name of the method. The method name and parameter list together form the method signature.

4) Parameter type: The parameter is like a placeholder. When the method is called, values ​​are passed to the parameters. This value is called an actual parameter or variable. The parameter list refers to the parameter type, order and number of parameters of the method. Parameters are optional and methods can contain no parameters.

5) Method body: The method body contains specific statements that define the function of the method.

##For example:

public static int age(int birthday){...}

There can be multiple parameters:

static float interest(float principal, int year){...}

Note: In some Methods in other languages ​​refer to procedures and functions. A method that returns a non-void return value is called a function; a method that returns a void return value is called a procedure.

Example

The following method contains 2 parameters num1 and num2, and it returns the maximum value of these two parameters.

/** 返回两个整型变量数据的较大值 */public static int max(int num1, int num2) {
int result;
if (num1 > num2)
result = num1;
else
result = num2;
return result; }

Method call

Java supports two ways to call methods, choose according to whether the method returns a value.

When a program calls a method, control of the program is given to the called method. Control is returned to the program when the return statement of the called method is executed or the method body closing bracket is reached.

When a method returns a value, the method call is usually treated as a value. For example:

int larger = max(30, 40);

If the method return value is void, the method call must be a statement. For example, the method println returns void. The following call is a statement:

System.out.println("Welcome to Java!");

Example

The following example demonstrates how to define a method and how to call it:

public class TestMax {
 /** 主方法 */
public static void main(String[] args) {
int i = 5;
int j = 2;
int k = max(i, j);
System.out.println("The maximum between " + i +
" and " + j + " is " + k);
}
/** 返回两个整数变量较大的值 */
public static int max(int num1, int num2) {
int result;
if (num1 > num2) result = num1;
else
result = num2;
return result; }}

The above example compiles and runs the results As follows:

The maximum between 5 and 2 is 5

This program contains main method and max method. The Main method is called by the JVM. Other than that, the main method is no different from other methods.

The header of the main method is unchanged, as shown in the example, with the modifiers public and static, returns a void type value, the method name is main, and takes a String[] type parameter . String[] indicates that the parameter is an array of strings.

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