Java Interview Questions
9 Apr, 2007
- What is the purpose of finalization? - The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.
- What is the difference between the Boolean & operator and the && operator? - If an expression involving the Boolean & operator is evaluated, both operands are evaluated. Then the & operator is applied to the operand. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. The && operator is then applied to the first and second operands. If the first operand evaluates to false, the evaluation of the second operand is skipped.
9 Apr, 2007
- How are commas used in the intialization and iteration parts of a for statement? - Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.
- What is an abstract method? - An abstract method is a method whose implementation is deferred to a subclass.
- What value does read() return when it has reached the end of a file? - The read() method returns -1 when it has reached the end of a file.
- Can a Byte object be cast to a double value? - No, an object cannot be cast to a primitive value.
9 Apr, 2007
- Can an object be garbage collected while it is still reachable? - A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected.
- Is the ternary operator written x : y ? z or x ? y : z ? - It is written x ? y : z.
- How is rounding performed under integer division? - The fractional part of the result is truncated. This is known as rounding toward zero.
- What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy? - The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented.
9 Apr, 2007
- Are enterprise beans allowed to use Thread.sleep()? - Enterprise beans make use of the services provided by the EJB container, such as life-cycle management. To avoid conflicts with these services, enterprise beans are restricted from performing certain operations: Managing or synchronizing threads
- Is it possible to write two EJB’s that share the same Remote and Home interfaces, and have different bean classes? if so, what are the advantages/disadvantages? - It’s certainly possible. In fact, there’s an example that ships with the Inprise Application Server of an Account interface with separate implementations for CheckingAccount and SavingsAccount, one of which was CMP and one of which was BMP.
9 Apr, 2007
- Can the primary key in the entity bean be a Java primitive type such as int? - The primary key can’t be a primitive type–use the primitive wrapper classes, instead. For example, you can use java.lang.Integer as the primary key class, but not int (it has to be a class, not a primitive)
- What’s new in the EJB 2.0 specification? - Following are the main features supported in EJB 2.0: Integration of EJB with JMS, Message Driven Beans, Implement additional Business methods in Home interface which are not specific for bean instance, EJB QL.
