Java扩展类一团糟

Question

I don't know what pot I was smoking when I posted the original, but I came to my senses and came up with this. I am not an experienced coder, but the entire post was made mostly as a question that for the most part has been answered. I now know classes can't have code directly in them, and more so about the core structure.

class Shape {

    public static void ShapeAttemptTwo()
    {
        class Circle extends Shape
            {
                public static CircleAttemptTwo()
                {
                int pi = 3.14;
                int r=4;
                }
            }
        class Rectangle extends Shape
        {
                public static Rectangle()
                {
                int l = 14;
                int b = 10;
                int z = l*b;
                }
        }
        class Square extends Shape
        {
            public static Square()
            {
            int a = 11;
            System.out.println(a * a);
            }
        }

// Java code 7, invalid method declare, return type required. (public static //CircleAttemptTwo()) // I'm lost on this one, could I have some help? // and reached end of file while parsing }, confusing to me.

/EDIT THANK YOU VERY MUCH. The constructive crit. really helped, as I ended up with a lot of knowledge and my final code was

class Shape {

public static void ShapeAttemptTwo()
{
    class Circle extends Shape
        {
            public static CircleAttemptTwo()
            {
            int pi = 3.14;
            int r=4;
            }
        }
    class Rectangle extends Shape
    {
            public static Rectangle()
            {
            int l = 14;
            int b = 10;
            int z = l*b;
            }
    }
    class Square extends Shape
    {
        public static Square()
        {
        int a = 11;
        System.out.println(a * a);
        }
    }

Answer 1

You're doing several things wrong:

1) Your "static main()" belongs inside a class

2) You can only have one "public class" per module.

SUGGESTED CHANGE:

public abstract class Shape 
{

    public static void main(String[] args)  {
      Shape rectangle = new Rectangle (14, 10);
      System.println ("rectangle's area=" + rectangle.getArea ());
      ...
    }

}

class Circle extends Shape  {
   ...
}

class Rectangle extends Shape  {

   int l;
   int b;

   public Rectangle (int l, int b) {
     this.l = l;
     this.b = b;
   }

   public int getArea () {
     return l * b;
   }
}
...

Answer 2

Are you joking? You're missing basic knowledges of Java:

1) Method yea doesn't have a return type.

2) There's a code directly inside the class Rectangle, not in method.

3) There's a code directly inside the class Square, not in method.

4) You're using very strange and weird code-style and formatting. Update : Formatting has been fixed.

2nd Update :

1) Code has been changed and it's formatted wrong again.

2) There are three static methods without defined return type.

Here are some more informations related on the topic.

Answer 3

Aside from the errors Tomas pointed out:

5) You forgot the word class in the Square declaration.

6) You cannot declare a public class directly inside a method. Java does allow you to declare classes, called "local classes" inside methods. However, I'm not sure if that's what you really want to do; if you do, you can only use Circle inside your main method, so you're not really creating a hierarchy. Anyway, when you declare a local class, it can't have public , protected , or private keywords on it, so that explains the first error message you're seeing.

Based on the second post: Every method has to have a return type; if you don't actually want the method to return anything, the return type should be void . Thus:

public static void CircleAttemptTwo() 
{
    //int pi = 3.14;  should be
    double pi = 3.14;
    int r=4;
}

However, constructors don't need a return type, but they can't be static . So public Square() and public Rectangle() are OK. CircleAttemptTwo doesn't match the class name, so it isn't a constructor.

"reached end of file" usually means you're missing a } , as you did here.

And 3.14 isn't an integer.

Answer 4

You need to change

int pi = 3.14;

to

double pi = 3.14; 

Also, static method is in wrong place.