Java classes and interfaces

An interface can inherit from multiple interfaces

interface C extends A, B {}
Note: At this time, the keywords extends
A and B are both interfaces

A class can implement multiple interfaces

class D implements A,B,C{}
Note: At this time, the keywords implements
A, B, and C are all interfaces

But a class can only inherit from one class, not multiple classes

class B extends A{}

While inheriting a class, you can also inherit an interface

class E extends D implements A,B,C{}

JDK instance:

public class ArrayList<E> extends AbstractList<E>
        implements List<E>, RandomAccess, Cloneable, java.io.Serializable

---

Reference documents:
1. https://blog.csdn.net/xuyukun121/article/details/51105951