Without Book Interview Questions and Answers | Online Test | Moct Test
Download Android App in your Android Device from Google Play Store
- Search for "Withoutbook Practice Exam Test" in Mobile/Tablet Play Store
Institute Training Search by Name or Email

Exams Attended

Make Homepage

Bookmark this page

Subscribe Email Address

Core Java Interview Questions and Answers

Ques 146. Why can't I say just abs() or sin() instead of Math.abs() and Math.sin()?

Ans. The import statement does not bring methods into your local name space. It lets you abbreviate class names, but not get rid of them altogether. That's just the way it works, you'll get used to it. It's really a lot safer this way.
However, there is actually a little trick you can use in some cases that gets you what you want. If your top-level class doesn't need to inherit from anything else, make it inherit from java.lang.Math. That *does* bring all the methods into your local name space. But you can't use this trick in an applet, because you have to inherit from java.awt.Applet. And actually, you can't use it on java.lang.Math at all, because Math is a '??final'?? class which means it can't be extended.

Is it helpful? Add Comment View Comments
Ques 147. Why are there no global variables in Java?
Ans. Global variables are considered bad form for a variety of reasons: Adding state variables breaks referential transparency (you no longer can understand a statement or expression on its own: you need to understand it in the context of the settings of the global variables), State variables lessen the cohesion of a program: you need to know more to understand how something works. A major point of Object-Oriented programming is to break up global state into more easily understood collections of local state, When you add one variable, you limit the use of your program to one instance. What you thought was global, someone else might think of as local: they may want to run two copies of your program at once. For these reasons, Java decided to ban global variables.
Is it helpful? Add Comment View Comments
Ques 148. What does it mean that a class or member is final?
Ans. A final class can no longer be subclassed. Mostly this is done for security reasons with basic classes like String and Integer. It also allows the compiler to make some optimizations, and makes thread safety a little easier to achieve. Methods may be declared final as well. This means they may not be overridden in a subclass. Fields can be declared final, too. However, this has a completely different meaning. A final field cannot be changed after it's initialized, and it must include an initializer statement where it's declared. For example, public final double c = 2.998; It's also possible to make a static field final to get the effect of C++'s const statement or some uses of C's #define, e.g. public static final double c = 2.998;
Is it helpful? Add Comment View Comments
Ques 149. What does it mean that a method or class is abstract?
Ans. An abstract class cannot be instantiated. Only its subclasses can be instantiated. You indicate that a class is abstract with the abstract keyword like this:
	public abstract class Container extends Component {
Abstract classes may contain abstract methods. A method declared abstract is not actually implemented in the current class. It exists only to be overridden in subclasses. It has no body. For example,
	public abstract float price();
Abstract methods may only be included in abstract classes. However, an abstract class is not required to have any abstract methods, though most of them do. Each subclass of an abstract class must override the abstract methods of its superclasses or itself be declared abstract.
Is it helpful? Add Comment View Comments
Ques 150. What is a transient variable?
Ans. transient variable is a variable that may not be serialized.
Is it helpful? Add Comment View Comments

Most helpful rated by users:

©2016 WithoutBook