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Core Java Interview Question, Interview Question

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Core Java Interview Question Page 16

     

Question: Which containers may have a MenuBar?

Answer: Frame

Question: How are commas used in the intialization and iterationparts of a for statement?

Answer: Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.

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 wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.

Question: What is an abstract method?

Answer: An abstract method is a method whose implementation is deferred to a subclass.

Question: How are Java source code files named?

Answer: A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined

within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension.

Question: What is the relationship between the Canvas class and the Graphics class?

Answer: A Canvas object provides access to a Graphics object via its paint() method.

Question: What are the high-level thread states?

Answer: The high-level thread states are ready, running, waiting, and dead.

Question: What value does read() return when it has reached the end of a file?

Answer: The read() method returns -1 when it has reached the end of a file.

Question: Can a Byte object be cast to a double value?

Answer: No, an object cannot be cast to a primitive value.

Question: What is the difference between a static and a non-static inner class?

Answer: A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.

Question: What is the difference between the String and StringBuffer classes?

Answer: String objects are constants. StringBuffer objects are not.

Question: If a variable is declared as private, where may the variable be accessed?

Answer: A private variable may only be accessed within the class in which it is declared.

Question: What is an object's lock and which object's have locks?

Answer: An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.

Question: What is the Dictionary class?

Answer: The Dictionary class provides the capability to store key-value pairs.

Question: How are the elements of a BorderLayout organized?

Answer: The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.

Question: What is the % operator?

Answer: It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.

Question: When can an object reference be cast to an interface reference?

Answer: An object reference be cast to an interface reference when the object implements the referenced interface.

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Posted on: April 18, 2011

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