一例看懂封装继承多态
本示例仅从属性及方法角度考虑
没有展示静态代码块、构造代码块、构造函数层面的关系
- 父类：
public class Father {
//1、非同名属性
String father_normalField = "father_normalField";
static String father_staticField = "father_staticField";
final String father_FINAL_FIELD = "father_FINAL_FIELD";
static final String father_STATIC_FINAL_FIELD = "father_STATIC_FINAL_FIELD";
//2、非同名方法
public String father_publicMeth() {
return "父类的father_publicMeth方法执行了";
}
String father_defaultMeth() {
return "父类的father_defaultMeth方法执行了";
}
protected String father_protectedMeth() {
return "父类的father_protectedMeth方法执行了";
}
private String father_privateMeth() {
return "父类的father_privateMeth方法执行了";
}
//3、同名属性
String rewrite_normalField = "father_rewrite_normalField";
static String rewrite_staticField = "father_rewrite_staticField";
final String rewrite_FINAL_FIELD = "father_rewrite_FINAL_FIELD";
static final String rewrite_STATIC_FINAL_FIELD = "father_rewrite_STATIC_FINAL_FIELD";
//4、同名方法
public String rewrite_publicMeth() {
return "父类的father_rewrite_publicMeth方法执行了";
}
String rewrite_defaultMeth() {
return "父类的father_rewrite_defaultMeth方法执行了";
}
protected String rewrite_protectedMeth() {
return "父类的father_rewrite_protectedMeth方法执行了";
}
private String rewrite_privateMeth() {
return "父类的father_rewrite_privateMeth方法执行了";
}
}- 子类：
class Son extends Father {
//1、非同名属性
String son_normalField = "son_normalField";
static String son_staticField = "son_staticField";
final String son_FINAL_FIELD = "son_FINAL_FIELD";
static final String son_STATIC_FINAL_FIELD = "son_STATIC_FINAL_FIELD";
//2、非同名方法
public String son_publicMeth() {
return "子类的son_publicMeth方法执行了";
}
String son_defaultMeth() {
return "子类的son_defaultMeth方法执行了";
}
protected String son_protectedMeth() {
return "子类的son_protectedMeth方法执行了";
}
private String son_privateMeth() {
return "子类的son_privateMeth方法执行了";
}
//3、同名属性
String rewrite_normalField = "son_rewrite_normalField";
static String rewrite_staticField = "son_rewrite_staticField";
final String rewrite_FINAL_FIELD = "son_rewrite_FINAL_FIELD";
static final String rewrite_STATIC_FINAL_FIELD = "son_rewrite_STATIC_FINAL_FIELD";
//4、同名方法
public String rewrite_publicMeth() {
return "子类的son_rewrite_publicMeth方法执行了";
}
String rewrite_defaultMeth() {
return "子类的son_rewrite_defaultMeth方法执行了";
}
protected String rewrite_protectedMeth() {
return "子类的son_rewrite_protectedMeth方法执行了";
}
private String rewrite_privateMeth() {
return "子类的son_rewrite_privateMeth方法执行了";
}
}- 测试：
class ExtendsTest {
public static void main(String[] args) {
Father father = new Father();
Son son = new Son();
System.out.println("==============================封装==============================");
//1.1、父类调用自己的属性
//非同名
System.out.println(father.father_normalField);
System.out.println(father.father_staticField);
System.out.println(father.father_FINAL_FIELD);
System.out.println(father.father_STATIC_FINAL_FIELD);
//同名
System.out.println(father.rewrite_normalField);
System.out.println(father.rewrite_staticField);
System.out.println(father.rewrite_FINAL_FIELD);
System.out.println(father.rewrite_STATIC_FINAL_FIELD);
//1.2、父类调用自己的非私有方法
//非同名
System.out.println(father.father_publicMeth());
System.out.println(father.father_defaultMeth());
System.out.println(father.father_protectedMeth());
//同名
System.out.println(father.rewrite_publicMeth());
System.out.println(father.rewrite_defaultMeth());
System.out.println(father.rewrite_protectedMeth());
//2.1、子类调用自己的属性
//非同名
System.out.println(son.son_normalField);
System.out.println(son.son_staticField);
System.out.println(son.son_FINAL_FIELD);
System.out.println(son.son_STATIC_FINAL_FIELD);
//同名
System.out.println(son.rewrite_normalField);
System.out.println(son.rewrite_staticField);
System.out.println(son.rewrite_FINAL_FIELD);
System.out.println(son.rewrite_STATIC_FINAL_FIELD);
//2.2、子类调用自己的非私有方法
//非同名
System.out.println(son.son_publicMeth());
System.out.println(son.son_defaultMeth());
System.out.println(son.son_protectedMeth());
//同名
System.out.println(son.rewrite_publicMeth());
System.out.println(son.rewrite_defaultMeth());
System.out.println(son.rewrite_protectedMeth());
System.out.println("==============================继承==============================");
//1、子类继承父类属性
//非同名
System.out.println("子类继承父类：" + son.father_normalField);
System.out.println("子类继承父类：" + son.father_staticField);
System.out.println("子类继承父类：" + son.father_FINAL_FIELD);
System.out.println("子类继承父类：" + son.father_STATIC_FINAL_FIELD);
//同名
System.out.println("子类继承父类：" + son.rewrite_normalField);
System.out.println("子类继承父类：" + son.rewrite_staticField);
System.out.println("子类继承父类：" + son.rewrite_FINAL_FIELD);
System.out.println("子类继承父类：" + son.rewrite_STATIC_FINAL_FIELD);
//2、子类继承父类方法
//非同名
System.out.println("子类继承父类：" + son.father_publicMeth());
System.out.println("子类继承父类：" + son.father_defaultMeth());
System.out.println("子类继承父类：" + son.father_protectedMeth());
//同名
System.out.println("子类继承父类：" + son.rewrite_publicMeth());
System.out.println("子类继承父类：" + son.rewrite_defaultMeth());
System.out.println("子类继承父类：" + son.rewrite_protectedMeth());
System.out.println("==============================多态==============================");
Father son2Father = son;//向上转型
System.out.println("--------------------向上转型--------------------");
//1.1父类
System.out.println("父类：" + son2Father.father_normalField);
System.out.println("父类：" + son2Father.father_staticField);
System.out.println("父类：" + son2Father.father_FINAL_FIELD);
System.out.println("父类：" + son2Father.father_STATIC_FINAL_FIELD);
System.out.println("父类：" + son2Father.father_publicMeth());
System.out.println("父类：" + son2Father.father_defaultMeth());
System.out.println("父类：" + son2Father.father_protectedMeth());
//1.2子类 父类类型不能访问子类特有属性
//1.3重写
System.out.println("动态绑定：" + son2Father.rewrite_normalField);
System.out.println("动态绑定：" + son2Father.rewrite_staticField);
System.out.println("动态绑定：" + son2Father.rewrite_FINAL_FIELD);
System.out.println("动态绑定：" + son2Father.rewrite_STATIC_FINAL_FIELD);
System.out.println("重写：" + son2Father.rewrite_publicMeth());
System.out.println("重写：" + son2Father.rewrite_defaultMeth());
System.out.println("重写：" + son2Father.rewrite_protectedMeth());
Son son2Father_2Son = (Son) son2Father;
System.out.println("--------------------向下转型--------------------");
//2.1父类
System.out.println("父类：" + son2Father_2Son.father_normalField);
System.out.println("父类：" + son2Father_2Son.father_staticField);
System.out.println("父类：" + son2Father_2Son.father_FINAL_FIELD);
System.out.println("父类：" + son2Father_2Son.father_STATIC_FINAL_FIELD);
System.out.println("父类：" + son2Father_2Son.father_publicMeth());
System.out.println("父类：" + son2Father_2Son.father_defaultMeth());
System.out.println("父类：" + son2Father_2Son.father_protectedMeth());
//2.2子类
System.out.println("子类：" + son2Father_2Son.son_normalField);
System.out.println("子类：" + son2Father_2Son.son_staticField);
System.out.println("子类：" + son2Father_2Son.son_FINAL_FIELD);
System.out.println("子类：" + son2Father_2Son.son_STATIC_FINAL_FIELD);
System.out.println("子类：" + son2Father_2Son.son_publicMeth());
System.out.println("子类：" + son2Father_2Son.son_defaultMeth());
System.out.println("子类：" + son2Father_2Son.son_protectedMeth());
//2.3重写
System.out.println("动态绑定：" + son2Father_2Son.rewrite_normalField);
System.out.println("动态绑定：" + son2Father_2Son.rewrite_staticField);
System.out.println("动态绑定：" + son2Father_2Son.rewrite_FINAL_FIELD);
System.out.println("动态绑定：" + son2Father_2Son.rewrite_STATIC_FINAL_FIELD);
System.out.println("重写：" + son2Father_2Son.rewrite_publicMeth());
System.out.println("重写：" + son2Father_2Son.rewrite_defaultMeth());
System.out.println("重写：" + son2Father_2Son.rewrite_protectedMeth());
}
}- 运行结果：
