What is the Set interface ?

Correct Answer: If you need to support random access, without inserting or removing elements from any place other than the end, then ArrayList offers the optimal collection If, however, you need to frequently add and remove elements from the middle of the list and only access the list elements sequentially, then LinkedList offers the better implementation

Correct Answer: To use an iterator to traverse through the contents of a collection, follow these steps: - Obtain an iterator to the start of the collection by calling the collections iterator() method - Set up a loop that makes a call to hasNext() Have the loop iterate as long as hasNext() returns true - Within the loop, obtain each element by calling next()

Correct Answer: Use Interfaces when? - You see that something in your design will change frequently - If various implementations only share method signatures then it is better to use Interfaces - You need some classes to use some methods which you don't want to be included in the class, then you go for the interface, which makes it easy to just implement and make use of the methods defined in the interface Use Abstract Class when? - If various implementations are of the same kind and use common behavior or status then abstract class is better to use - When you want to provide a generalized form of abstraction and leave the implementation task with the inheriting subclass - Abstract classes are an excellent way to create planned inheritance hierarchies They're also a good choice for nonleaf classes in class hierarchies

Correct Answer: Overriding means changing behavior of methods of base class in derive class by overriding the base class methods If class A is a base class with method ?calculate? and class B inherits class A, thus derives method ?calculate? of class A The behavior of ?calculate? in class B can be changed by overriding it

Correct Answer: :: is the scope resolution operator When local variable and global variable are having same name, local variable gets the priority C++ allows flexibility of accessing both the variables through a scope resolution operator

Correct Answer: SimpleTimeZone is a concrete subclass of TimeZone class The TimeZone class represents a time zone, that is to be used with Gregorian calendar The SimpleTimeZone is created by using the base time zone offset from GMT time zone ID and rules, for starting and ending the time of daylight

Correct Answer: Java applications can call code written in C, C++, or assembler This is sometimes done for performance and sometimes to access the underlying host operating system or GUI API using the JNI The steps for doing that are: First write the Java code and compile it Then create a C header file Create C stubs file Write the C code Create shared code library (or DLL) Run application

Correct Answer: Autoboxing is the process of converting a primitive type data into its corresponding wrapper class object instance Example: Integer number = new Integer (100); // number is now refers to the object 100 Unboxing is the process of converting a wrapper instance into a primitive type Example: Integer number = new Integer (100); int num = number;// without type casting number would be changed into int type

Correct Answer: A Monitor defines a lock and condition variables for managing concurrent access to shared data The monitor uses the lock to ensure that only a single thread inactive in the monitor code at any time A monitor allows only one thread to lock an object at once

Correct Answer: Dealing with primitives as objects is easier at times Most of the objects collection store objects and not primitive types Many utility methods are provided by wrapper classes To get these advantages we need to use wrapper classes As they are objects, they can be stored in any of the collection and pass this collection as parameters to the methods Features of the Java wrapper Classes: - Wrapper classes convert numeric strings into numeric values - The way to store primitive data in an object - The valueOf() method is available in all wrapper classes except Character - All wrapper classes have typeValue() method This method returns the value of the object as its primitive type