移动数组到不同的 class

Question

so im trying to get values of an array to a different class and to do stuff there. But i keep getting all those errors. Ive tried out so many things but it doesnt work. Basically i want each position of an arrray assign a value and pull these numbers to a different class and maybe later compare them. Its a simplified code of mine. I would thank anyone who can change the code so i dont get the error messages, i would appreciate if you could keep it as close to this as possible, because my code is very long and i want to get it to different classes to minimize the main class. Thanks in advance. <3

package Vasu;
public class First {

    public int n = 5;
    public int m = 0;
    long[] arr = new long[n];

    public static void main(String[] args) {

        Second C = new Second();  // cannot make a static reference in a non static field 
        arr[n - m] = m;           // "
        C.rules(arr[n - m]);      // "
        m++;

    }
}
//-----------------------------------------
package Vasu;

import java.util.Arrays;

public class Second {
    public double rule;

    public void rules(long[] arr) {
        if (arr[n - m] > 2) { // m and n cant be resolved into a variable
            rule=1;
            System.out.println("Array: " + Arrays.toString(arr));
        }
    }
}

Answer 1

Your error is that you pass a long variable instead of long array in line C.rules(arr[n - m]); , try pass the parameter C.rules(arr); (without the [nm] ).

Answer 2

In main() , you cannot access n , m , and arr because they are non-static. This could be "fixed" by changing them to static:

public class First {

    public static int n = 5;
    public static int m = 0;
    public static long[] arr = new long[n];

    public static void main(String[] args) {
        Second C = new Second();
        arr[n - m] = m;
        C.rules(arr);
        m++;
    }
    
}

I used quotes around "fixed" because we don't know how these values are being used in the larger context of your program. This may be fine, or it may break other parts...we'd have to understand a lot more about your program to make that call.

Note that when calling c.rules(arr) , we simply pass the name of the array. The syntax you were trying to use with c.rules(arr[n - m]) was passing a single value, while the method expects a reference to an entire array.

In class Second, we can now access n and m by preceding them with their class name, as in First.n and First.m . This is what the static designation allows you to do:

public class Second {

    public double rule;

    public void rules(long[] arr) {
        if (arr[First.n - First.m] > 2) {
            rule=1;
            System.out.println("Array: " + Arrays.toString(arr));
        }
    }
    
}

An alternative approach would be to pass both n and m to rules() along with the array. With that approach, however, you would not be able to change n and m and have those changes be reflected back in class First.

If you can't have n , m , and arr as static members, then you need to create an instance of First within main() to access those members. Doing so would also mean you could pass a reference to First into Second and access the values that way.

These are tough design decisions that we can't make for you without a better understanding of your app.

You definitely need to master what it means to be static , or you're not going to progress very far with this problem.