How to implement Java dynamic binding mechanism

1. The process of dynamic binding:

Example:

public class Son extends Father  Son son = new Son();3 son.method();

1. First, the compiler searches for the corresponding class based on the declared type and method name of the object (Son) and its parent class (Father)'s "method table", find all method methods whose access attributes are public.

There may be multiple methods named method, but the parameter types or numbers are different.

2. Then, find the exact matching method based on the "signature" of the method.

The name and parameter list of a method are called the signature of the method.

In versions prior to Java SE 5.0, when overriding a parent class method, the return type must be the same. When a subclass overrides a superclass method, its return type is now allowed to be defined as a subtype of the original type.

public Father getFather(){...} //父类中的方法  public Son getFather(){...} //子类覆盖父类中的getFather()方法

3. If it is a private, static, final method or constructor, the compiler clearly knows which method to call, and this calling method is called "static calling".

4. Call the method.

If the method() method is defined in the subclass Son, the corresponding method in the subclass will be called directly; if the corresponding method is not defined in the subclass Son, then method() will be found in its parent class. method.

2. Demo

1. Subclass overrides the method in the parent class and calls the method in the subclass

public class Father{      public void method(){          System.out.println("父类方法："+this.getClass());    }  }  public class Son extends Father{      public void method(){          System.out.println("子类方法"+this.getClass());  }  public static void main(String[] args){      Father instance = new Son();      instance.method();      }  }  //结果：子类方法：class Son

2. Subclass There is no overriding method in the parent class, so go to the parent class to find the corresponding method

public class Father{      public void method(){          System.out.println("父类方法："+this.getClass());      }  }  public class Son extends Father{      public static void main(String[] args){          Father instance = new Son();          instance.method();       }  }  //结果：父类方法：class Son

3. Dynamic binding is only for object methods and is invalid for attributes. Because properties cannot be overridden.

public class Father{      public String name = "父亲属性";      }  public class Son extends Father{      public String name = "孩子属性";       public static void main(String[] args){          Father instance = new Son();          System.out.println(instance.name);      }  }  //结果：父亲属性

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