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How to write functions in java

angryTom
Release: 2019-11-14 13:38:53
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How to write functions in java

How to write functions in java

The function composition of java is: (Recommended tutorial: java tutorial)

访问修饰符 返回值 函数名(形式参数)
{
	函数内容;
}
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Method to call the function:

Function name (the value or variable that needs to be passed to the 'formal parameter')

The type of data passed must be consistent with the data type of the formal parameters

It can be divided into four types according to whether there is a return value and whether there are formal parameters.

1. No return value and no parameters

void A()
{
}
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2. There is a return value and no parameters

int B()//返回值为int类型
{
}
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3. No return value and parameters

void C(int m)//接受int类型的参数 并把参数的值赋值给m
{
}
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4. There is a return value and parameters

int D(int n)
{
}
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Example:

public class Test1
{	
		int i;//定义变量
		int j;
		public void p()//定义一个访问修饰符为公有的方法P 
		{
			i=2;
			j=3;
		}
		public void pp(int m)//定义一个访问修饰符为公有的有一个参数的方法pp
		{
			j=m;
		}
		void show()//定义一个访问修饰符为默认(不写就是默认)的方法show
		{
			System.out.println("i="+i);//这里可以直接写i,因为它跟变量i在同一个类里面。
			System.out.println("j="+j);
		}
	public static void main(String args[])
	{
		
		Test1 aa = new Test1(); //实例化 Test1类,并取名为aa
		aa.p();//调用aa中的p方法
		aa.show();//调用aa中的show方法
		//也可以不调用aa.show(),自己输出数字
		System.out.println("i="+aa.i);//必须是aa.i,因为这个输出函数没有跟i在同一个类里面,只有实例化的对象aa中才有i这个变量。
		//aa.pp();//这样调用是错误的,因为调用的是带参数的函数,所以函数也要写一个参数。
		//aa.pp(1.222);//这样调用是错误的,因为它需要传递的参数类型跟函数接受的参数类型不一致。
		aa.pp(10);//这样就把10传给了pp函数里的m
		System.out.println("j="+aa.j);//这样输出的就是10
	}
}
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