JavaSE review diary: interface, javase review diary Interface

JavaSE review diary: interface, javase review diary Interface

/** Interface * Reference Data Type: * class, interface, array; ** interface is a reference data type, which can be considered as a special class, it is designed to solve the problem of weak functions caused by no multi-inheritance. A class can only have one parent class, but this class can implement multiple interfaces; ** the interface can also be seen as a class with only abstract methods, that is, all methods of the interface must be implemented. * The keyword declared by the interface is interface, instead of class; the inheritance keyword extends of a common class also becomes implements (Implementation). * However, extends serves the same purpose as ordinary classes, just to differentiate them; * ** 1 defines the interface Syntax: * [modifier list] interface name {} * 2 content in the interface: * can only be a constant (public static final constant name) and abstract METHODS * 3 abstract methods do not require abstract modification. By default, they are public (not required) * 4 interfaces can be considered as a special abstract Class is completely abstract. No common method * 5 interfaces do not have constructor methods, that is, interfaces cannot be instantiated. * 6 A class can implement multiple interfaces, however, you can only inherit one class * 7 Non-abstract class implementation interface. You need to implement all methods of the interface (rewrite/overwrite) * What About the abstract class implementation interface? * Abstract class implementation interface, which can be any: 0 ~ N ** 8 interfaces: * can be inherited. In addition, interfaces can also be inherited. In contrast, a class can only inherit a single ** constant and static data: * Initialization is performed when classes are loaded, but static data can be assigned multiple times. ** constant: public static final must be used to declare constants in interfaces, these can be omitted. * naming method: naming with uppercase letters and underscores. ** Note: The above section must differentiate the "inheritance" between interfaces ", "Implementation" between classes and interfaces, "inheritance" of classes and classes; */public class JavaSE {public static void main (String [] args) {F f = new F (); f. m1 (); f. m2 (); f. m3 (); f. m4 () ;}} interface A {// interface A public void m1 () ;}interface B {// interface B public void m2 ();} interface C {// interface C void m3 (); // the public of the method in the interface can be omitted;} interface D extends A, B, C {// The interface inherits multiple void m4 ();} class MyClass implements B, C {// The implementation of common classes on the Interface public void m2 () {System. out. println ("override B interface's m2 () method");} public void m3 () {System. out. println ("override the m3 () method of the C interface") ;}} abstract class E implements D {// implement public static final int A = 10 for the interface of the abstract class; // constant declaration method char C = '中'; public void m1 () {} public void m2 () {} public void m3 () {} public void m4 () {}} class F extends E {// all methods of E need to be overwritten public void m1 () {System. out. println ("override m1 () method");} public void m2 () {System. out. println ("override m2 () method");} public void m3 () {System. out. println ("override m3 () method");} public void m4 () {System. out. println ("overwriting the m4 () method in D ");}}