The Java Language in Java

Generation QR Code in Java The Java Language

The Java Language
Create QR Code 2d Barcode In Java
Using Barcode generator for Java Control to generate, create QR Code 2d barcode image in Java applications.
Scan QR-Code In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
Using instanceof
Bar Code Drawer In Java
Using Barcode drawer for Java Control to generate, create barcode image in Java applications.
Bar Code Reader In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
Sometimes, knowing the type of an object during run time is useful For example, you might have one thread of execution that generates various types of objects, and another thread that processes these objects In this situation, it might be useful for the processing thread to know the type of each object when it receives it Another situation in which knowledge of an object s type at run time is important involves casting In Java, an invalid cast causes a run-time error Many invalid casts can be caught at compile time However, casts involving class hierarchies can produce invalid casts that can be detected only at run time For example, a superclass called A can produce two subclasses, called B and C Thus, casting a B object into type A or casting a C object into type A is legal, but casting a B object into type C (or vice versa) isn t legal Because an object of type A can refer to objects of either B or C, how can you know, at run time, what type of object is actually being referred to before attempting the cast to type C It could be an object of type A, B, or C If it is an object of type B, a runtime exception will be thrown Java provides the run-time operator instanceof to answer this question The instanceof operator has this general form: objref instanceof type Here, objref is a reference to an instance of a class, and type is a class type If objref is of the specified type or can be cast into the specified type, then the instanceof operator evaluates to true Otherwise, its result is false Thus, instanceof is the means by which your program can obtain run-time type information about an object The following program demonstrates instanceof:
QR Maker In Visual C#
Using Barcode encoder for .NET framework Control to generate, create QR Code JIS X 0510 image in .NET applications.
Encoding QR Code 2d Barcode In VS .NET
Using Barcode creator for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
// Demonstrate instanceof operator class A { int i, j; } class B { int i, j; } class C extends A { int k; } class D extends A { int k; } class InstanceOf { public static void main(String args[]) { A a = new A(); B b = new B(); C c = new C(); D d = new D();
QR Code JIS X 0510 Creation In .NET Framework
Using Barcode maker for .NET framework Control to generate, create QR-Code image in .NET applications.
Making QR Code In Visual Basic .NET
Using Barcode generator for .NET framework Control to generate, create QR-Code image in Visual Studio .NET applications.
13:
Barcode Encoder In Java
Using Barcode drawer for Java Control to generate, create barcode image in Java applications.
UPC - 13 Maker In Java
Using Barcode drawer for Java Control to generate, create EAN-13 Supplement 5 image in Java applications.
I / O , A p p l e t s , a n d O t h e r To p i c s
UPC Symbol Generator In Java
Using Barcode creation for Java Control to generate, create GS1 - 12 image in Java applications.
Barcode Generator In Java
Using Barcode generator for Java Control to generate, create barcode image in Java applications.
if(a instanceof A) Systemoutprintln("a if(b instanceof B) Systemoutprintln("b if(c instanceof C) Systemoutprintln("c if(c instanceof A) Systemoutprintln("c
Delivery Point Barcode (DPBC) Maker In Java
Using Barcode printer for Java Control to generate, create Postnet 3 of 5 image in Java applications.
Scanning UPCA In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
is instance of A"); is instance of B"); is instance of C"); can be cast to A");
UPC-A Generator In VS .NET
Using Barcode drawer for ASP.NET Control to generate, create UPC Symbol image in ASP.NET applications.
European Article Number 13 Scanner In Visual Basic .NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET framework applications.
if(a instanceof C) Systemoutprintln("a can be cast to C"); Systemoutprintln(); // compare types of derived types A ob; ob = d; // A reference to d Systemoutprintln("ob now refers to d"); if(ob instanceof D) Systemoutprintln("ob is instance of D"); Systemoutprintln(); ob = c; // A reference to c Systemoutprintln("ob now refers to c"); if(ob instanceof D) Systemoutprintln("ob can be cast to D"); else Systemoutprintln("ob cannot be cast to D"); if(ob instanceof A) Systemoutprintln("ob can be cast to A"); Systemoutprintln(); // all objects can be cast to Object if(a instanceof Object) Systemoutprintln("a may be cast to if(b instanceof Object) Systemoutprintln("b may be cast to if(c instanceof Object) Systemoutprintln("c may be cast to if(d instanceof Object) Systemoutprintln("d may be cast to } }
Barcode Creation In .NET Framework
Using Barcode generator for Reporting Service Control to generate, create barcode image in Reporting Service applications.
Code 128A Generator In None
Using Barcode maker for Microsoft Excel Control to generate, create USS Code 128 image in Excel applications.
Object"); Object"); Object"); Object");
Decoding ANSI/AIM Code 39 In .NET Framework
Using Barcode scanner for Visual Studio .NET Control to read, scan read, scan image in VS .NET applications.
Data Matrix ECC200 Recognizer In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
The output from this program is shown here: a is instance of A b is instance of B
Part I:
The Java Language
c is instance of C c can be cast to A ob now refers to d ob is instance of D ob now refers to c ob cannot be cast to D ob can be cast to A a b c d may may may may be be be be cast cast cast cast to to to to Object Object Object Object
The instanceof operator isn t needed by most programs, because, generally, you know the type of object with which you are working However, it can be very useful when you re writing generalized routines that operate on objects of a complex class hierarchy
Copyright © OnBarcode.com . All rights reserved.