Java Class Description

Overloading and Overriding

Overloading: Same class, same method name, other parts different

Overriding: Parent-child class, same method name, (same name, two small, one big) same parameter list, return value, exception type, modifier

Interface and Abstract Class

Feature	Abstract Class	Interface
Inheritance	Can only inherit one abstract class	Can implement multiple interfaces
Method Implementation	Can have implemented methods and abstract methods	Methods are abstract by default, can have default methods and static methods
Member Variables	Can have instance variables and static variables	Can only have constants (public static final)
Constructors	Can have constructors	Cannot have constructors
Access Modifiers	Can have multiple access modifiers	Methods are public by default （Java 9 introduced private)
Usage Scenarios	Suitable for sharing code, providing basic implementation	Suitable for expressing behavioral specifications, supporting multiple implementations

• Code from: https://www.cnblogs.com/zimug/p/13806592.html

Java 8 Interface New Features

CustomInterface.java

interface CustomInterface {

    void abstractMethod();  //Abstract methods cannot be private

    static void staticMethod() {
        privateStaticMethod(); //public static method can call private static method
        System.out.println("Static method called");
    }

    default void defaultMethod() {
        privateMethod(); //Can call private method in interface
        privateStaticMethod(); //Can call private static method in interface
        System.out.println("Normal method called");
    }

    // this only can use java 9 or later version
    private void privateMethod() {
        System.out.println("private method called");
    }

    // this only can use java 9 or later version
    private static void privateStaticMethod() {
        System.out.println("private static method called");
    }
}

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