Step1: Logon to www.pmi.org. Login with your username and password
Step2: On the Home Page, click View PDU and then click Report PDU.

Step3: Select a PDU category

Step4:Fill the dates, name and check the relevant categories.
Step5:Fill the provider details like if QAI hosted the event.
Step6:Mention the number of PDUs you want to claim. There are categories and limits in each category
Step7:Finally check the I agree this claim is accurate and Submit.

You will receive an email saying the PDU have been submitted and another one saying approved. I got the two emails pretty quickly. So kudos to PMI for a neat system for submitting the PDUs.

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Humphrey’s work at Software Engineering Institute (SEI) at Carnegie Mellon University later led to development of the Capability Maturity Model(SEI-CMM)

Watts Humphrey died few days back at his home in Sarasota, Florida. He was fighting cancer.

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Step 2: Use the wizard (click Get Started” button) and a simple form appears.

Step 3:Enter the RSS feeds URL and the wizard will create a default layout

Step 4: Upload a picture as your icon

Step 5:Upload a picture as your logo, this will be displayed in the second row in your app’s view. Size limitations do irk but make sense.

Step 6: Enter some meta data(information abt yourself and what site has). Check checkboxes that ask that this content is your IP(property).

Step 7: Preview in emulator(simulated mobile screen) and you are done.

Step 8: Submit for approval….usually takes complete 24hours.

Watch out for the next post on how to create an app for Android in Java

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mailto: techbhaigiri@gmail.com

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public class MyFactory {
  private static volatile MyFactory instance;
  public static MyFactory getInstance (Connection conn) throws IOException {
    if (instance == null) {
      synchronized (MyFactory.class) {
        if (instance == null)
          instance = new MyFactory (conn);
      }
    }
    return instance;
  }
}

The double checked locking paradigm ensures that only the first call to the getInstance() method will go into the synchronized block. During that call, since the instance object is null, the code will go into the synchronized block and create the object. The second check makes sure that if two clients invoke the method at the same time, they will not end up creating two objects.

Any subsequent calls will simply return the instance object created earlier, without going into the synchronized block.

If the instance variable is not declared volatile, this would not work because the variable’s value might be cached by a thread, in which case a thread might not know if the variable’s value has changed.

Also Read:

Javamex Tutorial

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A: NavigableSet extends the SortedSet interface and adds navigation methods for reporting closest matches for given search targets.

TreeSet implements this interface.

1.       headSet() – Returns a view of the portion of this set whose elements are strictly less than toElement.
2.       tailSet() –    Returns a view of the portion of this set whose elements are greater than or equal to fromElement.
3.       lower() – Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
4.       higher() – Returns the least element in this set strictly greater than the given element, or null if there is no such element.
5.       floor() –   Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.
6.       ceiling() – Returns the least element in this set greater than or equal to the given element, or null if there is no such element.
7.       descendingSet() – Returns a reverse order view of the elements contained in this set.

Java API documentation

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Q: What is the Externalizable interface?
A: Externalizable interface extends the Serializable interface, and is used where we want a custom serialized form. Only the identity of the class of an Externalizable instance is written in the serialization stream and it is the responsibility of the class to save and restore the contents of its instances. The writeExternal and readExternal methods of the Externalizable interface are implemented by a class to give the class complete control over the format and contents of the stream for an object and its supertypes.

When an Externalizable object is reconstructed, an instance is created using the public no-arg constructor, and then the readExternal method called.

Q: What is a weak reference?
A: A weak reference that isn’t strong enough to force an object to remain in memory. In other words, once this object is not being referenced by any other strong references, then it can be garbage collected.

WeakReference wr = new WeakReference (myObject);
wr.get ()  // returns the referred object (myObject)


If you use an object as a key in an ordinary HashMap, that object cannot be collected until the mapping is removed from the Map; WeakHashMap allows you to use an object as a Map key without preventing that object from being garbage collected.

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Q: What is a soft reference?
A: Soft references are generally retained if memory is available. If however, the JVM is running short of memory then the soft references can be garbage collected.

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Q: What is a phantom reference?
A:  PhantomReference objects are always created associated with a ReferenceQueue. The reference will be enqueued when the collector determines that their referent can be reclaimed. These can now be used to perform pre-mortem activities before the object gets reclaimed actually.

WeakReferences are enqueued as soon as the object to which they point becomes weakly reachable. This is before finalization or garbage collection has actually happened; in theory the object could even be “resurrected” by an unorthodox finalize () method, but the WeakReference would remain dead.

PhantomReferences are enqueued only when the object is physically removed from memory, and the get () method always returns null specifically to prevent you from being able to “resurrect” an almost-dead object.

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Q: How can you stop the garbage collector from running?
A: You cannot stop the asynchronous garbage collector from running. There used to be a flag called noasyncgc, but it is not supported anymore. [link]

Creating a very large heap might help by delaying the garbage collection, but when it runs it will take a long time.

Q: Given a linked list, how can you find the middle element of the list?
A:

1.       Initialize two pointers to the front of the list
2.       In each iteration move one pointer by one element and the other pointer by two elements.
3.       When the second pointer reaches the end of the list, the first pointer will be at the middle element of the list.

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Q: How would you print the contents of a tree in level order?
A:

public void levelOrderTraversal () {
  Queue queue = new LinkedList ();
  queue.add (head);
  while (queue.size () > 0){
    Node node = queue.remove ();
    System.out.print (node.value + " ");
    if (node.left! = null) queue.add (node.left);
    if (node.right! = null) queue.add (node.right);
  }
  System.out.println ("");
}

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Q: In a list, a majority element is defined as an element that occurs more than n/2 times. Given an input list, how can you determine the majority element, if present?
A:

/**
* Returns the index of the majority element.
* If no majority element is present, then -1 is returned
*/
public static int majorityElement(int[] input){
  Map lookup = new HashMap();
  for(int i = 0; i < input.length; i++){
    Integer temp = lookup.get(input[i]);
    if (temp == null) temp = 1;
    else temp++;
    lookup.put(input[i], temp);
  }
  for(int i = 0; i < input.length; i++){
    int count = lookup.get(input[i]);
    if (count >= input.length/2 + 1) return i;
  }
  return -1;
}

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Q: How would you write an equals () method?
A:

1.       Compare the parameter object with the this object
2.       Check if the parameter object is of the correct type
3.       Cast the parameter object to the desired type
4.       Compare individual fields

public boolean equals(Object o) {
  if (o == this) return true;
  if (!(o instanceof PhoneNumber)) return false;
  PhoneNumber pn = (PhoneNumber)o;
  return pn.lineNumber == lineNumber &&
  pn.prefix == prefix && pn.areaCode ==   areaCode;
}

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Q: Given the following code,

Map map = new HashSet ();
map.put (new MyClass1 ("test"), object1);
map.put (new MyClass1 ("test"), object2);


How many objects will be present in the map after these statements? MyClass1 does not override the equals () and hashcode () method?

A: Two. The second object is not equal to the first one, so it will get stored as a different key.

Q: If you override hashcode (), do you need to override equals () also?
A: No. But if you override equals (), you certainly need to override hashcode ()

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Q: What are the different ways to create a thread?
A:

1. Extend the Thread class
2. Implement the Runnable interface. Create a Thread object using an object of the Runnable type.

Q: On a machine with a single processor, what advantage would you gain by having a multi-threaded application?
A: If one thread is waiting for some event like I/O or user input, then other threads can use the CPU. If all threads are computation intensive then having multiple threads might not be that helpful.

Q: What is the disadvantage of using the Spring framework?
A: Since all objects are created at runtime using the XML config, any errors in the bean definition will only be observed at runtime, and not at compile time.

Q: Explain the Java memory model?
A: Data is stored on the Heap and the Stack. There is a common heap for the entire process that is shared by all the threads. Any objects are created on the heap. Each thread gets its own stack, and local variables are created on the stack.

Q: Why would you use a distributed cache in your application?
A:
1.       In a standard java process on 32bit JVM, each process can only have a heap of 2 GB. If we want to store more data then it is a problem. By having a distributed cache we can bypass that limitation by being able to store as much data as possible. Now we have a large cloud of data running across multiple machines. This approach is very scalable. As the requirements grow, we just need to add more machines to the cache cluster.
2.       We wanted to store data inside memory instead of a database, for faster access to the data.

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Q: What are the new changes coming up in Java 7?
A:

1.       More predictable garbage collector. A new garbage collector that promises to achieve lower pause times and better predictability than the current CMS collector (VM-level feature)
2.       VM extensions to support the implementation of non-Java languages at performance levels near to that of the Java language itself
3.       Project Jigsaw – An implementation-specific, simple, low-level module system focused upon the goal of modularizing the JDK, and the application of that system to the JDK itself
4.       NIO2 - New APIs for filesystem access, scalable asynchronous I/O operations, socket-channel binding and configuration, and multicast datagrams. NIO2 uses operating system specific code to access files, directories and network resources, which leads to several speed improvements as well as extended capabilities which were not possible without NIO2. One of the notable improvements offered by NIO2 is the possibility of asynchronous access of (metadata) of files, enabling for example to execute code when a file is change without having to poll the file regularly for changes.
5.       Improved type inference for Generics, making it possible to write for example the following:
Map<String , List<String>> myMap = new HashMap<>();

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Q: How does garbage collection work?
A: The default collector has two generations - young and tenured. Most allocations are done in the young generation which is optimized for objects that have a shorter lifetime. Objects that survive several collections get moved to the tenured generation, which is collected less often as compared to the young generation.

Young generation – The collector is a copying collector with an option to collect the generation in parallel.
Tenured generation – The tenured generation is collected using a mark-sweep-compaction algorithm. There is an option to perform this collection concurrently.

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1.       Compare the parameter object with the this object
2.       Check if the parameter object is of the correct type
3.       Cast the parameter object to the desired type
4.       Compare individual fields

public boolean equals(Object o) {
    if (o == this) return true;
    if (!(o instanceof PhoneNumber)) return false;
    PhoneNumber pn = (PhoneNumber)o;
    return pn.lineNumber == lineNumber &&
           pn.prefix == prefix && pn.areaCode == areaCode;
}

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We will use a lookup table to store a count of how many times each element occurs. Once we create this table, we can use the lookup table to determine if any element has a corresponding count of more than (n/2 + 1).

	/**
	 * Returns the index of the majority element.
	 * If no majority element is present, then -1 is returned
	 * @param input
	 * @return
	 */
	public static int majorityElement(int[] input){
		Map lookup = new HashMap();
		for(int i = 0; i < input.length; i++){
			Integer temp = lookup.get(input[i]);
			if (temp == null) temp = 1;
			else temp++;
			lookup.put(input[i], temp);
		}

		for(int i = 0; i < input.length; i++){
			int count = lookup.get(input[i]);
			if (count >= input.length/2 + 1) return i;
		}
		return -1;
	}

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