Interfaces and inheritance: Classes that are not allowed to inherit

Sample Program

1  PublicFinalclassAddress2 {3     Privatefinal String detail;4     Privatefinal String postcode;5 6     //initializing two instance properties in a constructor method7      PublicAddress ()8     {9          This. Detail ="";Ten          This. Postcode =""; One     } A      PublicAddress (String detail, string postcode) -     { -          This. Detail =detail; the          This. Postcode =postcode; -     } -     //provides getter methods for only two instance properties -      PublicString getdetail () +     { -          return  This. Detail; +     } A  at      PublicString Getpostcode () -     { -          return  This. Postcode; -     } -     //override the Equals method to determine whether two objects are equal.  -      Publicboolean equals (Object obj) in     { -         if(obj instanceof Address) to         { +Address AD =(Address) obj; -             if( This. Getdetail (). Equals (Ad.getdetail ()) && This. Getpostcode (). Equals (Ad.getpostcode ())) the             { *                 return true; $             }Panax Notoginseng         } -         return false; the     } +      Public inthashcode () A     { the         returnDetail.hashcode () +Postcode.hashcode (); +     } -  $      Public Static voidMain (String args[]) $     { -Address A =NewAddress (); -Address B =NewAddress ("DSCFD","Fghgh"); the          -System. out. println ("A:"+a.getdetail () +a.getpostcode () +A.hashcode ());Wuyi          theSystem. out. println ("B:"+b.getdetail () +b.getpostcode () +B.hashcode ()); -          WuSystem. out. println (a.equals (b)); -     } About}

Results

Analysis:

Methods that are declared in final are not allowed to overwrite.

Variables declared in final are not allowed to change.

Using final, we can design a special "read-only" immutable class.

When an object of immutable class is created, the properties of this object cannot be changed, and new subclasses cannot be derived from this class. String is a typical example.

What is the use of immutable "classes"?

can be conveniently and safely used in multi-threaded environments, access to them can provide high performance without locking.

Instances in JDK: String

Interfaces and inheritance: Classes that are not allowed to inherit