Java & JEE books Page4 Posted on: April 1, 2008 at 12:00 AM
So, you want to set things to happen after a certain amount of time? Well, the setTimeout function can help you create some nice scripts that will use time delays to make things happen. Let's take a look at how to call the s
Java & JEE books Page4
So, you want to set things to happen after a certain amount of time? Well, the setTimeout function can help you create some nice scripts that will use time delays to make things happen. Let's take a look at how to call the setTimeout function:
The first parameter is a string, which is going to be the function you want to use. This function was named "myfunction()". The second parameter is a number. This number is going to be the number of milliseconds the browser should wait before executing your function. Above, we have 1000 milliseconds, which will be 1 second.
Concurrent Programming Using Java This is an introduction to using the Java programming language in concurrent or multithreaded applications. The context is the process synchronizatio
n material and related concurrent programming in operating systems courses as opposed to software engineering. Topics covered are race conditions when threads share data, critical sections, mutual exclusion, semaphores, monitors, message passing, the rendezvous, remote procedure calls, distributed or network programming, and parallel processing. Solutions to the classical problems talked about in operating systems courses (the dining philosophers, the bounded buffer producers and consumers, and the database readers and writers) are shown in Java. Also shown is how to animate algorithms using the command set of the Xtango animation interpreter, animator. Some of the animation examples can be viewed as applets.
Multi-Dispatch in the Java Virtual Machine Mainstream object-oriented languages, such as C++ and Java 1, provide only a restricted form of polymorphic methods, namely uni-receiver dispatch. In common programming situations, developers must work around this limitation. We describe how to extend the Java Virtual Machine to support
dispatch and examine the complications that Java imposes on multi-dispatch in practice.
Object-oriented (OO) languages provide powerful tools for expressing computations. One key abstraction is the concept of a type hierarchy which describes the relationships among types. Objects represent instances of these different types. Most existing object-oriented languages require each object variable to have a programmer-assigned static type. The compiler uses this information to recognize some coding errors. The principle of substitutability mandates that in any location where type T is expected, any sub-type of T is acceptable. But, substitutability allows that object variable to have a different
dynamic type at runtime.
A Research Framework for the Efficient Execution of Java
Bytecode Over the last few years, Java has rapidly become one of the most popular general purpose object-oriented (OO) programming languages. Java programs are compiled into class files which include type information and platform independent bytecode instructions. On a specific platform, a runtime system called a virtual
machine loads and links class files then executes bytecode instructions. The virtual machine collaborates with the standard class libraries to provide key services to Java programs, including threads and synchronization, automatic memory management (garbage collection), safety features (array bound checks, null pointer detection, code verification), reflection, dynamic class loading, and
more. Early Java virtual machines were simple bytecode interpreters.
An Operating System in Java for the Lego Mindstorms RCX Microcontroller The Lego Mindstorms is a Lego bricks based robotics toy series produced by the Lego Group, based on the ideas developed at the Massachusetts Institute of Technology in the Programmable Brick project. The heart of a Lego robot, the RCX microcontroller, hosts a Hitachi H8 microcontroller with 28 kilobytes of memory available for downloadable firmware and applications. In addition to the GUI based programming environment provided by Lego, a number of alternative programming environments have been developed for the RCX. However, these alternative programming environments are written in C, tightly bound to the hardware, and provide only relatively low level services. The strong hardware dependency makes it hard to debug programs; in practice, a hardware simulator is needed, and such a simulator does not yet exist in an open source form.
A Lego Mindstorms Robot consists of a programmable Lego brick, called the RCX, which contains three sensor inputs, three actuator outputs, four user buttons, a simple LCD display, an IR transceiver, and a Hitachi H8 microcontroller with 32 kilobytes of RAM, 4 kilobytes of which is used for interrupt vectors and other low level data. Normally, the RAM is used to host a firmware program, provided by Lego, which is used to interpret the actual user program.