Interview Questions for Java II
- What is the Vector class? The Vector class provides the capability to implement a growable array of objects. The main visible advantage of this class is programmer needn’t to worry about the number of elements in the Vector.
- What modifiers may be used with an inner class that is a member of an outer class? A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.
- If a method is declared as protected, where may the method be accessed? 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.
- What is an Iterator interface? The Iterator interface is used to step through the elements of a Collection.
- How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters? Unicode requires 16 bits, 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
- What is the difference between yielding and sleeping? Yielding means a thread returning to a ready state either from waiting, running or after creation, where as sleeping refers a thread going to a waiting state from running state. With reference to Java, when a task invokes its yield() method, it returns to the ready state and when a task invokes its sleep() method, it returns to the waiting state
- What are wrapper classes? Wrapper classes are classes that allow primitive types to be accessed as objects. For example, Integer, Double. These classes contain many methods which can be used to manipulate basic data types
- Does garbage collection guarantee that a program will not run out of memory? 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. The main purpose of Garbage Collector is recover the memory from the objects which are no longer required when more memory is needed.
- Name Component subclasses that support painting? The following classes support painting: Canvas, Frame, Panel, and Applet.
- What is a native method? A native method is a method that is implemented in a language other than Java. For example, one method may be written in C and can be called in Java.
- How can you write a loop indefinitely?
for(;;) //for loop
while(true); //always true
