how to make a method in java only callable by some classes
In Java, you can control access to a method by using access modifiers and package-private access. Here are a few ways to make a method only callable by some classes:

1. **Package-private access**: Declare the method without any access modifier (i.e., no `public`, `private`, or `protected` keyword). This way, the method can only be accessed by classes within the same package.
```java
// MyClass.java (in package com.example.mypackage)
class MyClass {
    void myMethod() {
        //...
    }
}

// OtherClass.java (in package com.example.mypackage)
class OtherClass {
    void someMethod() {
        MyClass myObject = new MyClass();
        myObject.myMethod(); // OK, same package
    }
}

// ExternalClass.java (in package com.example.otherpackage)
class ExternalClass {
    void someMethod() {
        MyClass myObject = new MyClass();
        myObject.myMethod(); // Compiler error, different package
    }
}
```
2. **Protected access with inheritance**: Declare the method as `protected`. This way, the method can only be accessed by subclasses of the class that declares the method.
```java
// MyClass.java
public class MyClass {
    protected void myMethod() {
        //...
    }
}

// MySubclass.java
public class MySubclass extends MyClass {
    void someMethod() {
        myMethod(); // OK, subclass
    }
}

// OtherClass.java

 In Java, you can control the visibility of methods using access modifiers. If you want to make a method callable only by some classes, you can use the `private` access modifier to make the method accessible only within its own class. However, if you want to allow access to a specific set of classes, you can use package-private or protected access modifiers.

Here's an example of how you can create a method that is only callable by some classes using the package-private access modifier:

Suppose you have two packages, `com.example.package1` and `com.example.package2`. You have a class `A` in `package1` that you want to allow access to a method `someMethod()` only from classes in `package2`.

In class `A`, you can define `someMethod()` with package-private access:
```java
package com.example.package1;

public class A {
    // some code here

    // package-private method
    void someMethod() {
        // some code here
    }
}
```
Now, any class in the same package `com.example.package1` can call `someMethod()` on an instance of `A`. However, classes in `com.example.package2` can also call `someMethod()` because it is package-private