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1. Review of access modifiers
==public: The classes, properties, and methods modified by it can not only be accessed across classes, but also across packages
==private: Can modify data members, constructors, methods, but cannot modify classes. The members modified by it can only be accessed by the class itself and cannot be accessed by subclasses
==protected: Can modify data members, constructors, and methods, but cannot modify classes. It can be accessed by members of this class, the same package, or its subclasses (if it is a subclass, it can cross packages)
==Default: No Add any modifier to only allow access in the same package
2. Code example
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package dog; public class Dog { // 公共的 public void publicMethod() { System.out.println("publicMethod"); } // 保护的 protected void protectedMethod() { // 被声明为protected的方法,可以被子类继承 System.out.println("protectedMethod"); } // 默认的 void defaultMethod() { System.out.println("defaultMethod"); } // 私有的 private void privateMethod() { // 这个方法只可以在类内部被调用 System.out.println("privateMethod"); } }
class T { public static void main(String[] args) { Dog d = new Dog(); // 可以访问 d.publicMethod(); // 可以访问 d.protectedMethod(); // 可以访问 d.defaultMethod(); // 可以访问 // d.privateMethod(); //私有的方法,不能被在类外访问 } }
//在上例的基础上,演示跨包的情况 package cat; //和dog 包不在一起 import dog.Dog; public class Cat { void test() { Dog dog = new Dog(); dog.publicMethod(); // 可以 // dog.protectedMethod(); 不可以 // dog.privateMethod(); 不可以 // dog.defaultMethod(); 不可以 } }##
//在前例的基础上,演示子类中的访问情况 class NiceDog extends Dog { void test() { Dog dog = new Dog(); dog.publicMethod(); // 可以 protectedMethod(); // 被protected修饰的成员,可以被继承过来,并这样调用 // dog.protectedMethod(); 不可以 // dog.privateMethod(); 不可以 // dog.defaultMethod(); 不可以 } }
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