(2) New methods in the interface

Methods added to the interface

1. JDK8 New interface in

stay JDK8 The interface is enhanced in , stay JDK8 Before

interface  The interface name {
    
     static const ;
     Abstract method ;
}

JDK8 After that, the interface was added , There can be The default method and Static methods

interface  The interface name {
    
 static const ;
 Abstract method ;
 The default method ;
 Static methods ;
}

2 The default method

2.1 Why add the default method

stay JDK8 Previously, there were only abstract methods and static constants in interfaces , There will be the following problems ：
If an abstract method is added to the interface , Then the implementation class must abstract this abstract method , It's not conducive to interface expansion

Add abstract method in interface , All implementation classes need to override this method , Not conducive to interface expansion

2.2 Interface default method format

The syntax format of the default method in the interface is

interface  The interface name {
    
     Modifier  default  return type   Method name {
    
     Method body ;
	}
}

2.3 The use of default methods in the interface

There are two ways to use the default methods in an interface

1. The implementation class calls the default method of the interface directly
2. The default method that implements the class override interface

3. Static methods

JDK8 Static methods are added to the interface in , The function is also to expand the interface

3.1 Rule of grammar

interface  The interface name {
    
     Modifier  static  return type   Method name {
    
     Method body ;
	}
}

3.2 Use of static methods

Static methods in an interface cannot be overridden in an implementation class , It can only be called through the interface type : The interface name . Static method name ();

If you want to trust your friends, you will have such questions Can the static methods in the interface be inherited Class implementation interface Can you call static methods in the interface

Direct address

4 The difference between the two is introduced

1. The default method is called by instance , Static methods are called by interface names
2. Default methods can be inherited , The implementation class can directly call the interface default method , You can also override interface default methods
3. Static methods cannot be inherited , An implementation class cannot override a static method of an interface , You can only call... With an interface name