Object-oriented (advanced)-basic concepts of interfaces

Object-oriented (advanced)-basic concepts of interfaces

An interface is the most important concept. An interface can be understood as a special class, which is composed of global constants and public abstract methods.
Interface Definition Format:

Interface interface name {
Global constant;
Abstract method;
}

Interface Definition:

Interface {
Public static final string author = "James ";
Public abstract void print (); //
Public abstract string getinfo (); // defines the abstract Method
}

Implementation interface:
1. Similar to abstract classes, interfaces must use subclasses. Subclass uses the implements keyword to implement the interface.
2. Implementation format:
Class subclass implements interface A, interface B ,...{
}

Implementation interface instance:

Interface {
Public static final string author = "James ";
Public abstract void print ();
Public abstract string getinfo ();
}
Abstract class B {
Public abstract void say ();
}
Class X extends B implements {
Public void say (){
System. Out. println ("Hello world !!! ");
}
Public String getinfo (){
Return "hello ";
}
Public void print (){
System. Out. println ("Author:" + author );
}
}
Public class interfacedemo01 {
Public static void main (string ARGs []) {
X = new x ();
X. Say ();
}
}

Interface inheritance

1. An interface cannot inherit an abstract class, but it can inherit multiple interfaces through the extends keyword.
2. Interface: interface sub-interface extends parent interface A, parent interface B ,...{}

Interface multi-inheritance instance

Interface {
Public static final string author = "James ";
Public abstract void printa ();
}
Interface B {
Public abstract void printb ();
}
Interface C extends a, B {
Public abstract void printc ();
}
Class X implements c {
Public void printa (){
System. Out. println ("A. Hello world !!! ");
}
Public void printb (){
System. Out. println ("B. Hello world !!! ");
}
Public void printc (){
System. Out. println ("C. Hello world !!! ");
}
}
Public class interfacedemo02 {
Public static void main (string ARGs []) {
X = new x ();
X. printa ();
X. printb ();
X. printc ();
}
}