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- Question
Which is true?
Options- A. "X extends Y" is correct if and only if X is a class and Y is an interface
- B. "X extends Y" is correct if and only if X is a class and Y is an interface
- C. "X extends Y" is correct if X and Y are either both classes or both interfaces
- D. "X extends Y" is correct for all combinations of X and Y being classes and/or interfaces
- Correct Answer
- "X extends Y" is correct if X and Y are either both classes or both interfaces
ExplanationA is incorrect because classes implement interfaces, they don't extend them. B is incorrect because interfaces only "inherit from" other interfaces. D is incorrect based on the preceding rules.
- 1. Which of the following is not used for commenting in java?
Options- A. //
- B. /* */
- C. /** */
- D. /** **/ Discuss
- // is a single line comment
- /* */ is commenting on one or more lines
- /** */ is documentation comment
- 2. What is the impact of declaring a method as final? Discuss
- 3. What is the access scope of a protected method? Discuss
- 4. How to define a constant variable in Java? Discuss
- 5. Is Java a pure object oriented language? Discuss
- 6. class Hell { public static void main(String[] args) { Integer i = 42; String s = (i<40)?"life":(i>50)?"base":"ball"; System.out.println(s); } }
Options- A. null
- B. ball
- C. base
- D. None Discuss
- 7. try { int x = Integer.parseInt("two"); } Which could be used to create an appropriate catch block?
Options- A. ClassCastException
- B. IllegalStateException
- C. NumberFormatException
- D. None Discuss
- 8. Difference between Java Beans & Servlets? Discuss
- 9. Just by seeing the signature of the bean how can you specity whether it is a Statefull of Stateless Session Bean? Discuss
- 10. How are this() and super() used with constructors? Discuss
Technology problems
Search Results
Correct Answer: /** **/
Explanation:
Correct Answer: A method declared as final can't be overridden A sub-class can't have the same method signature with a different implementation
Correct Answer: A protected method can be accessed by the classes within the same package or by the subclasses of the class in any package
Correct Answer: The variable should be declared as static and final So only one copy of the variable exists for all instances of the class and the value can't be changed also static final int PI = 214; is an example for constant
Correct Answer: Java uses primitive data types and hence is not a pure object oriented language
Correct Answer: ball
Explanation:
D is correct. This is a ternary nested in a ternary with a little unboxing thrown in.Both of the ternary expressions are false.
Correct Answer: NumberFormatException
Explanation:
C is correct. 'Integer.parseInt' can throw a NumberFormatException, and IllegalArgumentException is its superclass
Correct Answer: java bean is a reusable component, where as the servlet is the java program which extends the server capability
Correct Answer: The create method in a stateless bean cannot have arguments, and can only have a single method called create() While create in Stateful bean can have arguments and could be any method starting with create string eg create(arg1, arg2, ) Although it is not compiler checked but in stateless bean the ejb Passivate() and ejb Active() methods has to be empty as these functions are never called by EJB container As conceptually in stateful session bean we might need to store the clients information hence arguments in createare necessary While in stateless bean we don't hence no arguments are necessary It's intutive isn't intutive isn't I my life I haven't seen such a futuristic server programming tool as EJB
Correct Answer: Constructors use this to refer to another constructor in the same class with a different parameter list Constructors use super to invoke the superclass's constructor If a constructor uses super, it must use it in the first line; otherwise, the compiler will complain
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