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Home Java JavaBase How to write functions in java

How to write functions in java

Nov 14, 2019 pm 01:38 PM
java function

How to write functions in java

How to write functions in java

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

訪問修飾符 返回值 函數(shù)名(形式參數(shù))
{
	函數(shù)內(nèi)容;
}

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()
{
}

2. There is a return value and no parameters

int B()//返回值為int類型
{
}

3. No return value and parameters

void C(int m)//接受int類型的參數(shù) 并把參數(shù)的值賦值給m
{
}

4. There is a return value and parameters

int D(int n)
{
}

Example:

public class Test1
{	
		int i;//定義變量
		int j;
		public void p()//定義一個訪問修飾符為公有的方法P 
		{
			i=2;
			j=3;
		}
		public void pp(int m)//定義一個訪問修飾符為公有的有一個參數(shù)的方法pp
		{
			j=m;
		}
		void show()//定義一個訪問修飾符為默認(rèn)(不寫就是默認(rèn))的方法show
		{
			System.out.println("i="+i);//這里可以直接寫i,因為它跟變量i在同一個類里面。
			System.out.println("j="+j);
		}
	public static void main(String args[])
	{
		
		Test1 aa = new Test1(); //實例化 Test1類,并取名為aa
		aa.p();//調(diào)用aa中的p方法
		aa.show();//調(diào)用aa中的show方法
		//也可以不調(diào)用aa.show(),自己輸出數(shù)字
		System.out.println("i="+aa.i);//必須是aa.i,因為這個輸出函數(shù)沒有跟i在同一個類里面,只有實例化的對象aa中才有i這個變量。
		//aa.pp();//這樣調(diào)用是錯誤的,因為調(diào)用的是帶參數(shù)的函數(shù),所以函數(shù)也要寫一個參數(shù)。
		//aa.pp(1.222);//這樣調(diào)用是錯誤的,因為它需要傳遞的參數(shù)類型跟函數(shù)接受的參數(shù)類型不一致。
		aa.pp(10);//這樣就把10傳給了pp函數(shù)里的m
		System.out.println("j="+aa.j);//這樣輸出的就是10
	}
}

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