方法不能应用于给定类型

Question

public class HurdalQuentonA2Q1 {

  public static void main(String[] args) {

    double kgs ;

    double lbs ;

    double convertLBtoKG = convertLBtoKG(kgs, lbs) ;

  }
  static double convertLBtoKG(double lbs) {

    return lbs * 0.454 ; 


  }

  static double readWeight() {

    Scanner input = new Scanner(System.in) ;
    System.out.println("Enter your preferred system of weight measurement, k(for kg) or, p(for lb)") ;
    String userinput = input.nextLine() ;
      if(userinput == "p") {
        Scanner keyboard = new Scanner(System.in) ;
        System.out.println("Enter your dog's weight in lbs") ;
         double lbs = keyboard.nextDouble() ; 
          double kgs = convertLBtoKG ;

upon compilation an error pops up stating

method convertLBtoKG in class HurdalQuentonA2Q1 cannot be applied to given types
required: double
found: double,double

I have no clue whats causing this

Answer 1

convertLBtoKG method has only 1 parameter, but you are calling it with 2 parameters.

static double convertLBtoKG(double lbs) 

change your method call to:

double convertLBtoKG = convertLBtoKG(lbs) ;

Answer 2

Your convertLBtoKG method:

static double convertLBtoKG(double lbs) {

is defined as a method that needs one double parameter ( double lbs ) and returns a double (the double after the word static ). To use it, you have to call it in a way that's consistent with the profile: give it one double parameter, and then do something with the value of the method call, which will be what the method returns. Thus, instead of

double convertLBtoKG = convertLBtoKG(kgs, lbs) ;

you want

lbs = convertLBtoKG(kgs);  // THIS IS STILL WRONG, SEE BELOW

(don't say double lbs = ... since you already declared double lbs; earlier).

Also, you will need to assign something to kgs before you use it in the method call.

Although I tried to fix the line that was giving you the error, it's totally wrong, and it doesn't belong there. The code that actually does the conversion is in readWeight , but you never call readWeight . You need to add something to main that calls it. Then, in readWeight , instead of this line:

      double kgs = convertLBtoKG ;

this is where you would want to call the convert method:

      double kgs = convertLBtoKG(lbs);

I think you need to study carefully how the flow of a program works. Your main program has to call readWeight in order to get the code in readWeight called; the language doesn't automatically wire things together because you've put convertLBtoKG in both main and readWeight .

Answer 3

您的convertLBtoKG的函数声明仅允许传递一个参数，但同时传递lbs和kgs。

Answer 4

You are passing in two double values to a method which is only accepting a single double argument. Either overload the method to create one which accepts two doubles, or call it with the appropriate arguments.

Answer 5

Your methods get only 1 parameter double. But you called convertLBtoKG(kgs, lbs) 2 parameter in here.

Answer 6

upon compilation, the compiler will try to match the number of parameters and their type. In this case, you are calling with two parameters but accepting only one.