Java interface

{tabs-pane label="interface"}

interface Pure abstract interfaces that are more abstract than abstract classes , Because it can't even have fields . Because all methods defined by the interface default to public abstract Of , So these two modifiers don't need to be written （ The effect is the same whether you write or not ）.

// Comparison of abstract class methods
abstract class demo4_1{
public abstract void run();
public abstract String name();
}

interface demo4_1{
void run();
String getName();
}

interface demo4_1{
void run();
String getName();
}
interface demo4_1chou{
void run();
String name();
}
//class Realization interface Need to use implements keyword
class demo4_1_1 implements demo4_1{
private String name;
public demo4_1_1(String name){// Construction method
this.name=name;
}
@Override // Inherit
public void run() {// Methods in the parent class
System.out.println(this.name+" 1");
}
@Override
public String getName() {// Fields in parent class
// TODO Auto-generated method stub
return this.name;
}
}

One class can only inherit from another class , Cannot inherit from more than one class . however , A class can implement multiple interface, for example :

class demo4_1_2 implements demo4_1,demo4_1chou{
protected String name;
@Override
public void run() {}
@Override
public String getName() {
return this.name;}
@Override
public String name() {
return this.name;}
}

{/tabs-pane} {tabs-pane label=" The term "}

The term Pay attention to distinguishing terms ： Java The interface of refers specifically to interface The definition of , Represents an interface type and a set of method signatures , And programming interface generally refers to interface specification , Such as method signature , data format , Network protocol, etc .

{/tabs-pane} {tabs-pane label=" Interface inheritance extends"}

One interface Can inherit from another interface.interface Inherited from interface Use extends, It is equivalent to a method that extends the interface

// Interface inheritance extends
interface demo4_1_3 extends demo4_1{
void run();
String getName();
}

{/tabs-pane} {tabs-pane label="default Method "}

Implementation classes can be overridden default Method .default The purpose of the method is , When we need to add a method to the interface , It involves modifying all subclasses . If what's new is default Method , So subclasses don't have to be completely modified , Only need to overwrite the new method where it needs to be overwritten .

default Methods are different from ordinary methods of abstract classes . because interface No fields ,default Method cannot access field , Ordinary methods of abstract classes can access instance fields .

demo4_1 d=new demo4_1_4(" I'm the default method ");
d.run();

interface demo4_1{
//void run();
String getName();
default void run(){System.out.println(this.getName()+" run");}
}

class demo4_1_4 implements demo4_1{
private String name;
public demo4_1_4(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
}

{/tabs-pane}

This article altogether 425 Number of words , Average reading time ≈ 2 minute