How can I implement interface correctly?

I am doing homework of making a simple calculator using java and interface in java. but the class that implements java gives error saying

The public type BasicCalculator must be defined in its own file
The type BasicCalculator must implement the inherited abstract method calculate.mul(int, int)

how can I solve this? help me plz.
here is the code

interface calculate{
    public int add(int a, int b);
    public int sub(int a, int b);
    public int mul(int a, int b);
    public int div(int a, int b);
}

public class BasicCalculator implements calculate { 
    public int a;
    public int b;

    public int add(int a, int b) {
        return a + b;
    }

    public int subtract(int a, int b) {
        return a - b;
    }

    public int multiply(int a, int b) {
        return a * b;
    }

    public int division(int a, int b){
        return a/b;
    }
}

public class test {
    public static void main(String[] args) {
        calculate c= new BasicCalculator();
        c.add(5,6);
    }
}

>Solution :

There are a couple of issues here.

First, since BasicCalculator is a public class, it needs to be defined in its own file named BasicCalculator.java.

Second, the method names in BasicCalculator must match those you’re trying to implement in calcualte – i.e., sub, mul and div instead of subtract, multiply and division.