Wednesday, September 26, 2007

Java Interview Questions-8

Question: Which package has light weight components?
javax.Swing package. All components in Swing, except JApplet, JDialog, JFrame and JWindow are lightweight components.

Question: What are peerless components?
The peerless components are called light weight components.

Question: What is the difference between the Font and FontMetrics classes?
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.

Question: What happens when a thread cannot acquire a lock on an object?
If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available.

Question: 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.

Question: What classes of exceptions may be caught by a catch clause?
A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types.

Question: What is the difference between throw and throws keywords?
The throw keyword denotes a statement that causes an exception to be initiated. It takes the Exception object to be thrown as argument. The exception will be caught by an immediately encompassing try-catch construction or propagated further up the calling hierarchy. The throws keyword is a modifier of a method that designates that exceptions may come out of the method, either by virtue of the method throwing the exception itself or because it fails to catch such exceptions that a method it calls may throw.

Question: If a class is declared without any access modifiers, where may the class be accessed?
A class that is declared without any access modifiers is said to have package or friendly access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.

Question: What is the Map interface?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.

Question: Does a class inherit the constructors of its superclass?
A class does not inherit constructors from any of its superclasses.

Question: Name primitive Java types.
The primitive types are byte, char, short, int, long, float, double, and Boolean.

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