当我尝试调用方法“ calcArea”时，出现错误消息“无法从静态上下文中引用非静态方法calcArea（）”

Question

I've messed around with this for an hour now and can't get it to work. I've also looked this question up but the wording used in answers I've found haven't helped me at all.

Any help would be much appreciated.

Also, the invocation in question is at the very end of the program, inside main .

import java.util.Scanner;
public class Area {

Scanner input = new Scanner (System.in);
/**
 * @param args the command line arguments
 */
public static void areaTriangle (double height, double length){
   System.out.println((height * length) * .5);
}

public static void areaRectangle (double height, double length, 
        double width){
   System.out.println(height * length * width);
}

public static void areaCircle (double radius){
  System.out.println(Math.PI * (radius * radius));
}

  public void calcArea (){
    double i;
    System.out.println("Which shape's area would you like to calculate?: \n"
    + "Enter '1' for Triangle \n"
    + "Enter '2' for Rectangle \n"
    + "Enter '3' for Circle \n"
    + "Enter '0' to quit the program");

    i = input.nextDouble();

    if (i == 1)
    {
            System.out.print("Enter the height of your triangle: ");
            double height = input.nextDouble();

            System.out.print("Enter the height of your length: ");
            double length = input.nextDouble();

            areaTriangle(height, length);
    }
    else if ( i == 2)
    {
        System.out.print("Enter the height of your rectangle: ");
        double height = input.nextDouble();

        System.out.print("Enter the length of your rectangle: ");
        double length = input.nextDouble();

        System.out.print("Enter the width of your rectangle: ");
        double width = input.nextDouble();

        areaRectangle(height, length, width);
    }
    else if ( i == 3)
    {
        System.out.print("Enter the radius of your circle");
        double radius = input.nextDouble();

        areaCircle(radius);
    }
    else if ( i == 0)
        return;
    else
        System.out.println("Please input a number from 0 - 3");


  }

  public static void main(String[] args) {
    calcArea();
  }

}

Answer 1

put static in calcArea

public static void calcArea ()

or you can do this in your main

 public static void main(String[] args) {
     YourClassName variable= new YourClassName();
     variable.calcArea();
    }

just change the "YourClassName" to the name of your class and also you can change the variable object