One 、 Problem introduction

If you need to define a method to sum , This method can flexibly fulfill the following requirements ：

• Calculation 1 The sum of two data .
• Calculation 2 The sum of two data .
• Calculation 3 The sum of two data .
• Calculation n The sum of two data ,
• It can even support calling without receiving parameters . 

Two 、 effect

1. The transmission parameters are very flexible , convenient 、 No parameters can be passed ,
2. You can transfer a parameter Multiple parameters can be transferred
3. You can transfer an array
4. Variable parameters are essentially an array inside a method

Note on variable parameters ：

1. There can only be one variable parameter in a formal parameter list

2. Variable parameters must be placed at the end of the formal parameter list

Format ：

Format of variable parameters ： data type ... Parameter name

public class MethodDemo {
    public static void main(String[] args) {
        sum();//1. Don't pass parameters 
        sum(10);//2. You can pass a parameter 
        sum(10,20,30);//3. Multiple parameters can be passed 
        sum(new int[]{10,20,40,50});//4. You can transfer an array 
    }

    /**
     *  Be careful ： There can only be one variable parameter in a formal parameter list 
     * @param nums
     */
    public static void sum (int... nums){
        // Be careful ： Variable parameters are actually an array inside the method .nums
        System.out.println(" Element number ：" + nums.length);
        System.out.println(" Element content ：" + Arrays.toString(nums));
    }
}