What are the basic interfaces of Java Collections Framework ?

Correct Answer: - A process is an execution of a program, while a Thread is a single execution sequence within a process - A process can contain multiple threads A Thread is sometimes called a lightweight process

Correct Answer: There are three ways that can be used in order for a Thread to be created: A class may extend the Thread class A class may implement the Runnable interface An application can use the Executor framework, in order to create a thread pool The Runnable interface is preferred, as it does not require an object to inherit the Thread class In case your application design requires multiple inheritance, only interfaces can help you Also, the thread pool is very efficient and can be implemented and used very easily

Correct Answer: When an object is passed by value, this means that a copy of the object is passed Thus, even if changes are made to that object, it doesn?t affect the original value When an object is passed by reference, this means that the actual object is not passed, rather a reference of the object is passed Thus, any changes made by the external method, are also reflected in all places

Correct Answer: Dynamic method dispatch which is also known as runtime polymorphism is a process in which a call to an overridden method is resolved at runtime rather than at compile-time In this process, an overridden method is called through the reference variable of a superclass The determination of the method to be called is based on the object being referred to by the reference variable

Correct Answer: Dynamic binding is orthogonal to dynamic linking Binding refers to the linking of a procedure call to the code to be executed in response to the call Dynamic binding It is associated with polymorphism and inheritance, it(also known as late binding) means that the code associated with a given procedure call is not known until the time of the call at run-time

Correct Answer: The Big-O notation simply describes how well an algorithm scales or performs in the worst case scenario as the number of elements in a data structure increases The Big-O notation can also be used to describe other behavior such as memory consumption Since the collection classes are actually data structures, we usually use the Big-O notation to chose the best implementation to use, based on time, memory and performance Big-O notation can give a good indication about performance for large amounts of data

Correct Answer: Enumeration is twice as fast as compared to an Iterator and uses very less memory However, the Iterator is much safer compared to Enumeration, because other threads are not able to modify the collection object that is currently traversed by the iterator Also, Iteratorsallow the caller to remove elements from the underlying collection, something which is not possible with Enumerations

Correct Answer: 1 2 3

Explanation:

In argument[0] = args;, the reference variable arg[0], which was referring to an array with two elements, is reassigned to an array (args) with three elements.
Output:
$ javac main_arguments.java
$ java main_arguments
1 2 3

Correct Answer: Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes For example, converting an int to an Integer, a double to a Double, and so on If the conversion goes the other way, this is called unboxing

Correct Answer: A static variable in Java belongs to its class and its value remains the same for all its instances A static variable is initialized when the class is loaded by the JVM If your code tries to access a non-static variable, without any instance, the compiler will complain, because those variables are not created yet and they are not associated with any instance