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, a method can be made "private" or "protected" so that it can only be called by certain classes. To make a method private, it must be declared inside a class with the keyword "private", and the method must have the same name as the variable it is accessing. To make a method protected, it must be declared inside a class with the keyword "protected", and the method must have the same name as the class it is in.