方法 areEqualByThreeDecimalPlace(double, double) 对于 DecimalComparator 类型未定义

Question

My main java.

public class Main {
    
    DecimalComparator dc = new DecimalComparator();
    DecimalComparator rt = new DecimalComparator();
    

    public static void main(String[] args) {
        
            
        dc.areEqualByThreeDecimalPlace(1.256, 2.632);   
        
    }
    
}

My DecimalComparator code

public class DecimalComparator {

    public  void areEqualByThreeDecimalPlace(double num1,double num2) {
        
        String Str1 = String.format("%.3g%n",num1);
        
        System.out.println("The value of Str1"+Str1);
    }

}

and in Min.class I have error "The method areEqualByThreeDecimalPlace(double, double) is undefined for the type DecimalComparator"

Answer 1

Your main method is static. You cannot get a non-static instance of DecimalComparator from a static method. You have to get an instance of your Main class to get an instance of your DecimalConverter class.

Field names in Java always start with a lower-case character.

Here's the complete runnable code I used. I made your DecimalComparator class an inner class so I could post the code as one block.

public class DecimalComparatorMain {

    public static void main(String[] args) {
        DecimalComparatorMain dcm = new DecimalComparatorMain();
        DecimalComparator dc = dcm.new DecimalComparator();
        dc.areEqualByThreeDecimalPlace(1.256, 2.632);
    }

    public class DecimalComparator {

        public void areEqualByThreeDecimalPlace(double num1, double num2) {
            String str1 = String.format("%.3g%n", num1);
            System.out.println("The value of str1: " + str1);
        }

    }

}