The difference between abstract classes and interfaces

1. In common

Can contain abstract methods;

2. The difference between

  • An abstract class is a “class” that is usedclassDeclared as a keyword; An interface is another kind of data that is usedinterfaceDeclared as a keyword;
  • Abstract classes can have various properties with different permissions and modifiers, and can contain ordinary methods, abstract methods, or no ordinary methods at all, or no abstract methods at all. All members of the interface arepublicOf, all of the properties arestatic,finalBefore JDK 1.8, all methods were abstract;
  • The relationship between a common class and an abstract class is “inheritance”. When a common class inherits an abstract class, it has the obligation to rewrite the abstract method in the abstract class. In Java statements, the inheritance between classes is 1 to 1. The relationship between a common class and an interface is “implementation”. When a common class implements an interface, it is also obliged to rewrite all abstract methods in the interface. The implementation relationship between a class and an interface is 1-to-many, that is, a class can simultaneously implement several interfaces. Interfaces can also inherit from one another in a one-to-many relationship. That is, one interface can inherit from several interfaces at the same time.

3. Use experience/installation

Classes describe categories; Interface, is to describe the shape of patterns, behavior characteristics, norms, standards!

The relation between classes is A; The relationship between a class and an interface is has A.

public class Person { public String name; }
public class Student extends Person {}
public class Teacher extends Person {}

public class Animal {}public class Cat extends Animal {}

public interfacelearning{ voidTo learn (a parameter); }public interfaceteaching{}
public interfacedriving{ voidDriving (a parameter); }public class Person implementsStudy, teach, drive{} Person =newPerson(); The Person li si =new Person();
Copy the code

Attachment 1: Eclipse common shortcuts

Ctrl + Shift + F Formatting code (code layout)
Ctrl + Shift + O finishingimportStatements (add necessary, remove unnecessary)
Alt + up/down To move a single line of code, place the cursor on that line before operating. Move several lines of code, need to be checked before operation
Ctrl + Alt + Direction up/Direction down Copy several lines of code up/down in the same manner as moving the entire line
Alt + Shift + R To rename a variable or method in the current source file, select the entire name before performing the operation
Ctrl + D Deletes entire lines or lines of code in the same manner as moving entire lines of code

To be continued…