Programming Java 2 Micro Edition for Symbian OS 2004 (779882), страница 76
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These capabilities aremoving into mobile phones: the current phones only support VGA,however the next generation of mobile phones will have megapixelresolution cameras (indeed a number of Japanese cameras already do).Many of today’s mobile phones come with FM radios and in the futurewe are likely to see the inclusion of Digital Audio Broadcast radios. InKorea, people can now use their mobile phones for credit card purchases.The consequence will be an explosion in the amount of data users storeon their mobile phone: audio, video, images, email and messaging.
Thiswill amount to gigabytes of storage.So, we leave you with a simple challenge: to use your developmentskills, and the knowledge and insight that we hope you have gainedfrom this book, to create the next killer Java service or application onSymbian OS.Appendix 1CLDC Core LibrariesSystem Classesjava.lang.Classjava.lang.Objectjava.lang.Runtimejava.lang.Systemjava.lang.Threadjava.lang.Runnable (interface)java.lang.ThrowableInstances of Class represent classesand interfaces in a running application.The Object class is the root of classes.Every Java application has a singleinstance of the Runtime class, whichallows the application to interface withthe environment in which it is running.Note that the Exit() method alwaysthrows a java.lang.SecurityException.The System class contains severaluseful fields and methods and it cannotbe instantiated. Note that the Exit()method always throws a java.lang.SecurityException.A Thread is a unit of execution in aprogram.
Multiple threads may beexecuted concurrently.This interface should be implementedby any class which is intended to beexecuted as threads. A run() methodmust be defined by such a class.The Throwable class is the superclassof all errors and exceptions.Programming Java 2 Micro Edition on Symbian OS: A developer’s guide to MIDP 2.0. Martin de Jode 2004 Symbian Ltd ISBN: 0-470-09223-8424CLDC CORE LIBRARIESData Type Classesjava.lang.Booleanjava.lang.Bytejava.lang.Characterjava.lang.Integerjava.lang.Longjava.lang.Shortjava.lang.Stringjava.lang.StringbufferThe Boolean class wraps a value ofthe boolean primitive type in an object.The Byte class wraps a value of thebyte primitive type in an object.The Character wraps a value of thechar primitive type in an object.The Integer class wraps a value ofthe int primitive type in an object.The Long class wraps a value of thelong primitive type in an object.The Short class wraps a value of theshort primitive type in an object.The String class represents characterstrings.A StringBuffer implements amutable sequence of characters.Collection Classesjava.util.Vectorjava.util.Stackjava.util.Hashtablejava.util.Enumeration (interface)The Vector class implements an arrayof objects that can grow.The Stack class represents a last infirst out stack of objects.This class implements a hashtable,which maps keys to values.An object that implements theEnumeration interface generates aseries of elements, one at a time.Input/Output Classesjava.io.InputStreamjava.io.OutputStreamjava.io.ByteArrayInputStreamThis abstract class is the superclass ofall classes representing an input streamof bytes.This abstract class is the superclass ofall classes representing an outputstream of bytes.A ByteArrayInputStream has aninternal buffer that contains bytes thatmay be read from the stream.CALENDAR AND TIME CLASSESjava.io.ByteArrayOutputStreamjava.io.DataInput (interface)java.io.DataOutput (interface)java.io.DataInputStreamjava.io.DataOutputStreamjava.io.Readerjava.io.Writerjava.io.InputStreamReaderjava.io.OutputStreamReaderjava.io.PrintStream425This class implements an outputstream in which the data is written intoa byte array.The DataInput interface provides forreading bytes from a binary stream andreconstructing from them data in anyof the primitive types.The DataOutput interface providesfor converting data from any of theprimitive types to a series of bytes andwriting to a binary stream.A DataInputStream lets anapplication read primitive data typesfrom an underlying input stream in amachine-independent way.A DataOutputStream lets anapplication write primitive data typesto an output stream in a portable way.An abstract class for reading characterstreams.An abstract class for writing characterstreams.An InputStreamReader is a bridgefrom byte streams to character streams.It reads bytes and translates them intocharacters according to a specifiedcharacter encoding.An OutputStreamReader is abridge from character streams to bytestreams.
Characters written to it aretranslated into bytes according to aspecified character encoding.A PrintStream adds functionality toanother output stream, namely theability to print representations ofvarious data values conveniently.Calendar and Time Classesjava.util.CalendarThe Calendar is an abstract class forgetting and setting dates using a set ofinteger fields such as YEAR, MONTH,DAY, etc.426CLDC CORE LIBRARIESjava.util.Datejava.util.TimeZoneThe Date class represents a specificinstant in time with a millisecondprecision.The TimeZone class represents a timezone offset and also works out daylightsavings.Additional Utility Classesjava.util.Randomjava.lang.MathAn instance of this class is used togenerate series of pseudo-randomnumbers.The Math class contains methods forperforming basic numeric operations.Exception Classesjava.lang.Exceptionjava.lang.ClassNotFoundExceptionjava.lang.IllegalAccessExceptionjava.lang.InstantiationExceptionjava.lang.InterruptedExceptionjava.lang.RuntimeExceptionThe Exception class and itssubclasses are a form of Throwablethat indicates conditions that areasonable application might want tocatch.Thrown when an application tries toload in a class through its string nameusing the forName() method inClass class.Thrown when an application tries toload in a class but the executingmethod does not have access to theclass definition, because the class is inanother package and is not public.Thrown when an application tries tocreate an instance of a class using thenewInstance() method in Classclass, but cannot instantiate it becauseit is an interface or an abstract class orit doesn’t have a default constructor.Thrown when a thread is waiting,sleeping or otherwise paused andanother thread interrupts it.This is the superclass of exceptions thatcan be thrown during the normaloperation of the Java Virtual Machine.EXCEPTION CLASSESjava.lang.ArithmeticExceptionjava.lang.ArrayStoreExceptionjava.lang.ArrayIndexOutOfBoundsExceptionjava.lang.ClassCastExceptionjava.lang.IllegalArgumentExceptionjava.lang.IllegalThreadStateExceptionjava.lang.NumberFormatExceptionjava.lang.IllegalMonitorStateExceptionjava.lang.IndexOutofBoundsExceptionjava.lang.StringIndexOutOfBoundsExceptionjava.lang.NegativeArraySizeExceptionjava.lang.NullPointerExceptionjava.lang.SecurityExceptionjava.util.EmptyStackExceptionjava.util.NoSuchElementException427Thrown when an exceptionalarithmetic condition occurs.Thrown to indicate that an attempt hasbeen made to store the wrong type ofobject in an array of objects.Thrown to indicate that an array hasbeen accessed with an illegal index.Thrown to indicate that the code hasattempted to cast an object to asubclass of which it is not aninstance.Thrown to indicate that a method hasbeen passed an illegal or inappropriateargument.Thrown when starting a Thread forthe second time.Thrown when trying to read anInteger from a malformed String.Thrown to indicate that a thread hasattempted to wait on an object’smonitor or to notify other threadswaiting on an object’s monitor withoutowning the specified monitor.Thrown to indicate that an index ofsome sort (such as an index to anarray, to a string, or to a vector) is outof range.Thrown by the charAt() method inclass String and by other Stringmethods, to indicate that an index iseither negative or greater than or equalto the size of the string.Thrown if an application tries to createan array with negative size.Thrown when an application attemptsto use null in a case where an object isrequired.Thrown by the security manager toindicate a security violation.Thrown by methods in the Stack classto indicate that the stack is empty.Thrown by the methods of anEnumeration to indicate that thereare no more elements in theenumeration.428CLDC CORE LIBRARIESjava.io.EOFExceptionjava.io.IOExceptionjava.io.InterruptedIOExceptionjava.io.UnsupportedEncodingExceptionjava.io.UTFDataFormatExceptionSignals that an end of file or end ofstream has been reached unexpectedlyduring input.Signals that an I/O exception of somesort has occurred.Signals that an I/O operation has beeninterrupted.Signals that the character encoding isnot supported.Signals that a malformed UTF8 stringhas been read in a data input stream orby any class that implements the datainput interface.Error ClassesIn contrast to the exception classes, the error-handling capabilities ofCLDC are limited to just three:java.lang.Errorjava.lang.VirtualMachineErrorjava.lang.OutOfMemoryErrorError is a subclass of Throwablethat indicates serious problems that areasonable application may not try tocatch.Thrown to indicate that the Java VirtualMachine is broken or has run out ofthe resources necessary for it tocontinue operating.Thrown when the Java VirtualMachine cannot allocate an objectbecause it is out of memory and nomore memory can be made availableby the garbage collector.Catching an OutOfMemoryError is very good practice when developing for a resource-constrained device.
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