Java literacy interface Enumeration

Java literacy interface Enumeration
Java literacy interface Enumeration

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I. First recognized Enumeration

When I wrote network programming, I found this interface. It is amazing that it has never been used before. NetworkInterface. getNetworkInterfaces () returns the NetworkInterface object of the Enumeration carrier. Enumeration is an interface class in java. util. It encapsulates methods for Enumeration data sets in Enumeration. The Enumeration interface is not a data structure. However, it is very important for other data structures. The Enumeration interface defines a means to obtain continuous data from a data structure.

Note: The functions of this interface are the same as those of the Iterator interface. In addition, the Iterator interface adds an optional remove operation and uses a shorter method name. The Iterator interface rather than the Enumeration interface should be preferred for the new implementation. Ii. Use java. util Enumeration

Generally, the following two methods in Enumeration are used to print all elements in the vector:

(1)boolean hasMoreElements()
Test whether the enumeration contains more elements.

(2)E nextElement()
If this enumeration object has at least one available element, the next element of this enumeration is returned.

Usage 1:

Vec is an object that implements a Vector (SET) class through an interface. vec. elements () gets an element of a Vector (SET.

for(Enumeration e = vec.elements(); e.hasMoreElements();){

 System.out.println(e.nextElement()); 

}

Usage 2:

E is an object that implements the Enumeration interface

while (e.hasMoreElements()) {    Object o= e.nextElement();    System.out.println(o);}

The following is an example:

public class TestEnumeration{       public static void main(String[] args){              Vector v = new Vector();              v.addElement("Li");              v.addElement("YYY");              v.addElement("Brown");                           Enumeration e = v.elements();              while(e.hasMoreElements()){                     String value = (String)e.nextElement();                     System.out.println(value);              }       }}

You can see the following output

LiYYYBrown

Iii. demonstrate the use of the Enumeration Interface

Below we will implement this interface to complete a small function:

The MyDataStruct class is used to instantiate a simple enumeration object that can be provided to the data result object of the program.

1234567891011121314151617181920

class MyDataStruct{ String[] data; // Constructor MyDataStruct() { data = new String[4]; data[0] = "zero"; data[1] = "one"; data[2] = "two"; data[3] = "three"; } // Return an enumeration object to the application Enumeration getEnum() { return new MyEnumeration(0, data.length, data); }}

　　

The MyEnumeration class implements the Enumeration interface.

Class MyEnumeration implements Enumeration {int count; // counter int length; // The length of the stored array Object [] dataArray; // reference for storing data arrays // constructor MyEnumeration (int count, int length, Object [] dataArray) {this. count = count; this. length = length; this. dataArray = dataArray;} public boolean hasMoreElements () {return (count <length);} public Object nextElement () {return dataArray [count ++];}

Test MainClass

Class MainClass {public static void main (String [] args) {// instantiate MyDataStruct-type object MyDataStruct mySataStruct = new MyDataStruct (); // obtain the enumeration object Enumeration myEnumeration = mySataStruct that describes the object of myDataStruct type. getEnum (); // use the object loop to display each element of an object of the myDataStruct type while (myEnumeration. hasMoreElements () System. out. println (myEnumeration. nextElement ());}}

You can see the following output:

zeroonetwothree

4. Thank you for your knowledge sources and summary.

I. First recognized Enumeration

Ii. Use of functions

Iii. demonstrate the use of the Enumeration Interface

From: java Basics

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