java interview questions

Question: What is the purpose of the wait(), notify(), and notifyAll() methods?
Answer: The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to communicate each other.

Question: What is the Collections API?
Answer: The Collections API is a set of classes and interfaces that support operations on collections of objects.

Question: What is the List interface? 
Answer: The List interface provides support for ordered collections of objects.

Question: If a method is declared as protected, where may the method be accessed?
Answer: A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.

Question:  What is an Iterator interface?
Answer:  The Iterator interface is used to step through the elements of a Collection.

Question:  How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?
Answer: Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.

Question:  What is the difference between yielding and sleeping? 
Answer: When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.

Question:  Is sizeof a keyword? 
Answer:  The sizeof operator is not a keyword.

Question: What are wrapped classes?
Answer: Wrapped classes are classes that allow primitive types to be accessed as objects.

Question: Does garbage collection guarantee that a program will not run out of memory? 
Answer: No, it doesn't. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection.

Question: Name Component subclasses that support painting.
Answer: The Canvas, Frame, Panel, and Applet classes support painting.