📓3.8: Scope & Access
Table of Contents
📖 This page is a condensed version of CSAwesome Topic 3.8
Scope refers to where a variable can be accessed in a program.
Access modifiers determine which parts of a program can use a variable or method.
Variable Scope
- Local variables: Declared inside a method, only accessible within that method.
- Instance variables: Declared inside a class but outside any method, accessible to all methods in that class.
- Class (static) variables: Declared with
static, shared by all objects.
Example:
public class Example {
private int instanceVar = 10; // instance scope
public void method() {
int localVar = 5; // local scope
System.out.println(localVar);
}
}
Access Modifiers
public: Accessible from any other class.private: Accessible only within the same class.protected: Accessible within the same package and subclasses.- No modifier: Package-private (accessible only within the same package).
Example
public class Person {
public String name; // public: accessible anywhere
private int age; // private: only inside this class
public Person(String n, int a) {
name = n;
age = a;
}
public int getAge() { // provides controlled access
return age;
}
}
Best Practices
- Keep variables private and use getter/setter methods to control access.
- Use the most restrictive access modifier possible to reduce unintended interactions.
Summary
- Scope: Where a variable exists and can be used.
- Access modifiers: Control who can see or modify a variable or method.
- Favor
privatefor encapsulation and maintainability.