Java design pattern-Observer Pattern

When the product name and price in the online store change, the member must be notified automatically. Java API provides
The observer interface and the observable class implement the so-called observer mode.
The observable class allows other objects to be notified (implemented interface observer, observer) when changes occur ).
The following is an observer (product class ):
Import java. util .*;
Public class product extends observable {
Private string name; // Product Name
Private float price; // price

Public String getname () {return name ;}
Public void setname (string name ){
This. Name = Name;
//// Set the Change Point
Setchanged ();
Yyobservers (name); // notify the observer

}

Public float getprice () {return price ;}
Public void setprice (float price ){
This. Price = price;
//// Set the Change Point
Setchanged ();
Notifyobservers (new float (price ));

}

//// The following commands can be used to update and insert a database.
Public void savetodb (){
System. Out. println ("savetodb ");
}

}

The following are two observers:
Import java. util .*;
Public class nameobserver implements observer {

Private string name = NULL;
Public void Update (observable OBJ, object Arg ){
If (ARG instanceof string ){
Name = (string) ARG;
/// The value of the product name changes to the name
System. Out. println ("nameobserver: Name changet to" + name );

}

}
}

Import java. util .*;
Public class priceobserver implements observer {
Private float price = 0;
Public void Update (observable OBJ, object Arg ){
If (ARG instanceof float ){

Price = (float) Arg). floatvalue ();
　　
System. Out. println ("priceobserver: price changet to" + price );

}

}

}
Below are the test classes:
Public class test {

Public static void main (string ARGs []) {
Product = new product ();
Nameobserver nameobs = new nameobserver ();
Priceobserver priceobs = new priceobserver ();

/// Add the observer
Product. addobserver (nameobs );
Product. addobserver (priceobs );

Product. setname ("applet ");
Product. setprice (9.22f );

}
}
Running result:
C:/Java> JAVA Test
Nameobserver: Name changet to Applet
Priceobserver: price changet to 9.22

C:/Java>

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