Interview Questions and Multiple Choice Questions and Answers

how to insert your applets into FrontPage? | Java Applets

1. Place the class file in the directory containing the HTML document into which you want to insert the applet.
2. Copy the <applet>...</applet> tag from your applet implenientation or examples to the clipboard.
3. In FrontPage select the “HTML” tab from the lower left hand corner.
4. Paste the <applet>.. .</applet> tag in an appropriate place between the <body> and </body> tags. You’ll find a gray box with the aqua letter “J” in the “Normal” view indicating the the applet tag has been inserted.
5. To see the applet appearance select the “Preview” tab.

What is an Applet? Should applets have constructors? | Java Applets

Applets are small programs transferred through Internet, automatically installed and run as part of web-browser. Applets implements functionality of a client Applet is a dynamic and interactive program that runs inside a Web page displayed by a Java-capable browser. We don’t have the concept of Constructors in Applets. Applets can be invoked either through browser or through Appletviewer utility provided by JDK.

What is a working thread? | Java Threads

A working thread, more commonly known as a worker thread is the key part of a design pattern that allocates one thread to execute one task. When the task is complete, the thread may return to a thread pool for later use. In this scheme a thread may execute arbitrary tasks, which are passed in the form of a Runnable method argument, typically execute(Runnable). The runnable tasks are usually stored in a queue until a thread host is available to run them.

The worker thread design pattern is usually used to handle many concurrent tasks where it is not important which finishes first and no single task needs to be coordinated with another. The task queue controls how many threads run concurrently to improve the overall performance of the system. However, a worker thread framework requires relatively complex programming to set up, so should not be used where simpler threading techniques can achieve similar results.

What is a green thread? | Java Threads

A green thread refers to a mode of operation for the Java Virtual Machine (JVM) in which all code is executed in a single operating system thread. If the Java program has any concurrent threads, the JVM manages multi-threading internally rather than using other operating system threads.

There is a significant processing overhead for the JVM to keep track of thread states and swap between them, so green thread mode has been deprecated and removed from more recent Java implementations. Current JVM implementations make more efficient use of native operating system threads.

Which class is the wait() method defined in? | Java Threads

The wait() method is defined in the Object class, which is the ultimate superclass of all others. So the Thread class and any Runnable implementation inherit this method from Object. The wait() method is normally called on an object in a multi-threaded program to allow other threads to run. The method should should only be called by a thread that has ownership of the object's monitor, which usually means it is in a synchronized method or statement block.

What is the SwingUtilities.invokeLater(Runnable) method for? | Java Threads

The static utility method invokeLater(Runnable) is intended to execute a new runnable thread from a Swing application without disturbing the normal sequence of event dispatching from the Graphical User Interface (GUI). The method places the runnable object in the queue of Abstract Windowing Toolkit (AWT) events that are due to be processed and returns immediately. The runnable object's run() method is only called when it reaches the front of the queue.

The deferred effect of the invokeLater(Runnable) method ensures that any necessary updates to the user interface can occur immediately, and the runnable work will begin as soon as those high priority events are dealt with. The invoke later method might be used to start work in response to a button click that also requires a significant change to the user interface, perhaps to restrict other activities, while the runnable thread executes.

What is the volatile modifier for? | Java Threads

The volatile modifier is used to identify variables whose values should not be optimized by the Java Virtual Machine, by caching the value for example. The volatile modifier is typically used for variables that may be accessed or modified by numerous independent threads and signifies that the value may change without synchronization.

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Tuesday, 14 February 2012