required: double [] found: no arguments

问题:

Code:

 ArrayList <Integer> marks = new ArrayList();

 String output = "Class average:" + calculateAverage() + "\n" + "Maximum mark:" +  
 calculateMaximum() + "\n" +"Minimum mark:" + calculateMinimum() + "\n" + "Range of 
 marks:" + range;

 analyzeTextArea.setText(output);

 private double calculateAverage(double [] marks) {
 double sum = 0;
 for (int i=0; i< marks.length; i++) {
 sum += marks[i];
 }
 return sum / marks.length;
 }

Disregard the other things inside the string (minimum, maximum, and range) but for this line,

 String output = "Class average:" + calculateAverage() + "\n" + "Maximum mark:" +  
 calculateMaximum() + "\n" +"Minimum mark:" + calculateMinimum() + "\n" + "Range of 
 marks:" + range;

I get an error:

required: double []
found: no arguments

Why do I get this error and what should I change?

回答1:

You're calling the method calculateAverage this way: calculateAverage(), without any argument. But the method is declared this way:

private double calculateAverage(double [] marks) 

It thus needs one argument of type double[], but you don't pass anything.

回答2:

Look at this:

String output = "Class average:" + calculateAverage() + ...

What's that meant to be calculating the average of? You've got to provide the method with some data to average. The same is going to be true of calculateMaximum, calculateMinimum etc. Without any context, those methods can't do anything.

Where are your actual marks stored? Presumably you have some sort of variable storing the marks - so pass that. For example:

String output = "Class average:" + calculateAverage(actualMarks) + ...

... except obviously with the real variable, or whatever you're using to store the marks.

回答3:

private double calculateAverage(double [] marks) is the method declaration, so when its called it must have and argument of double array

eg:

calculateAverage(double_value_array);

回答4:

You can call it this way:

double d[] = {1, 2, 3};
double ret = calculateAverage(d);
System.out.println(ret);