Java inheritance polymorphism (override-> override (= overwrite), overload-> overload, polymorphism-> polymorphism)

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Package edu. javase. buffer;

Class demo1 {
Public demo1 (){
System. Out. println ("fun1 constend ");
}

Public demo1 (int I ){
System. Out. println ("fun1 int I constend:" + I );
}

// Overload (similar)
Public void fun1 (){
System. Out. println ("fun1 ");
}

Public void fun1 (int I, string s ){
System. Out. println ("fun1 int string ");
}

Public void fun1 (string S, int I ){
System. Out. println ("fun1 string int ");
}

Public int fun1 (int I ){
System. Out. println ("fun1 return int ");
Return I;
}

Public final void finalfun (){
System. Out. println ("fun1 finalfun ");
}
}

Class demo2 extends demo1 {
Public demo2 (){
Super (); // load the parent class Constructor
System. Out. println ("fun1 constend ");
}

Public demo2 (int I ){
Super (I); // load the parent class Constructor
System. Out. println ("fun2 int I constend:" + I );
}

// Overload (similar)
Public void fun2 (){
System. Out. println ("fun2 ");
}

Public void fun2 (int I, string s ){
System. Out. println ("fun2 int string ");
}

Public void fun2 (string S, int I ){
System. Out. println ("fun2 string int ");
}

Public int fun2 (int I ){
System. Out. println ("fun2 return int ");
Return I;
}

// Rewrite the inheritance relationship
// Public void fun1 (){
// System. Out. println ("2 rewrite fun1 ");
//}
}

Class demo3 extends demo2 {
Public demo3 (){
Super (); // load the parent class Constructor
System. Out. println ("fun1 constend ");
}

Public demo3 (int I ){
Super (I); // load the parent class Constructor
System. Out. println ("fun3 int I constend:" + I );
}

// Overload (similar)
Public void fun3 (){
System. Out. println ("fun3 ");
}

Public void fun3 (int I, string s ){
System. Out. println ("fun3 int string ");
}

Public void fun3 (string S, int I ){
System. Out. println ("fun3 string int ");
}

Public int fun3 (int I ){
System. Out. println ("fun3 return int ");
Return I;
}

// Rewrite the inheritance relationship
Public void fun1 (){
System. Out. println ("3 rewrite fun1 ");
}

Public void fun2 (){
System. Out. println ("3 rewrite fun2 ");
}

}

Public class Jicheng {
Public static void main (string [] ARGs ){
Demo1 d1 = new demo1 (1 );
D1.fun1 ();
System. Out. println ("~~~~~~~~~~~~~~ ");

Demo2 D2 = new demo2 (2 );
D2.fun1 (); // demo2 inherits all methods of the parent class demo1
D2.fun2 ();
System. Out. println ("~~~~~~~~~~~~~~ ");

Demo3 D3 = new demo3 (3 );
D3.fun1 (); // demo2 inherits all methods of the parent class demo1 and super parent classes.
D3.fun2 ();
D3.fun3 ();
System. Out. println ("~~~~~~~~~~~~~~ ");

Demo1 D11 = new demo2 (2 );
D11.fun1 (); // method in demo2 to override the method in demo1; otherwise, only the demo1 method is available.
System. Out. println ("------------");

Demo1 d111 = new demo3 (3 );
D111.fun1 (); // The method in demo1 must be rewritten in demo3; otherwise, only the demo1 method is available.
System. Out. println ("------------");

Demo2 D22 = new demo3 (2 );
D22.fun1 (1 );
D22.fun1 ();
D22.fun2 (2 );
D22.fun2 ();
D22.finalfun (); // In demo3, you must override the methods in the parent class. Otherwise, only all parent class methods are available. Other methods of your own cannot be called.
System. Out. println ("------------");
}/* Output:
Fun1 int I constend: 1
Fun1
~~~~~~~~~~~~~~
Fun1 int I constend: 2
Fun2 int I constend: 2
Fun1
Fun2
~~~~~~~~~~~~~~
Fun1 int I constend: 3
Fun2 int I constend: 3
Fun3 int I constend: 3
3 rewrite fun1
3 rewrite fun2
Fun3
~~~~~~~~~~~~~~
Fun1 int I constend: 2
Fun2 int I constend: 2
Fun1
------------
Fun1 int I constend: 3
Fun2 int I constend: 3
Fun3 int I constend: 3
3 rewrite fun1
------------
Fun1 int I constend: 2
Fun2 int I constend: 2
Fun3 int I constend: 2
Fun1 return int
3 rewrite fun1
Fun2 return int
3 rewrite fun2
Fun1 finalfun
------------

*///:~
}

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