General Java Questions II

Increases the capacity of this vector, if necessary, to ensure that it can hold at least

the number of components specified by the minimum capacity argument.

Parameters: 

minCapacity   the desired minimum capacity.

 What re the differences between classpath and import in the java application? 

Do I need to have the package in the classpath first before importing in a java

application or need not?

Answer: Classpath is an environment variable of your OS, you have to set it (or

better: Java sets it) to tell Java where to search for classes. 

You use import in a program to let Java search for the specified classes within the

classpath. This implies that the package must be in the classpath.

Stephan Effelsberg

 Q: What is difference between Iterator and Enumeration?

First of all Java FAQ Team wish you !!!HAPPY NEW YEAR!!! and then

Answer: from

http://java.sun.com/docs/books/tutorial/collections/interfaces/collection.html

The object returned by the iterator method deserves special mention. It is an Iterator,

which is very similar to an Enumeration, but differs in two respects: 

Iterator allows the caller to remove elements from the underlying collection during the

iteration with well defined semantics. 

Method names have been improved. 

The first point is important: There was no safe way to remove elements from a

collection while traversing it with an Enumeration. The semantics of this operation

were ill defined, and differed from implementation to implementation. 

The Iterator interface is shown below: 

public interface Iterator {

   boolean hasNext();

   Object next();

   void remove(); // Optional

}

The hasNext method is identical in function to Enumeration.hasMoreElements, and

the next method is identical in function to Enumeration.nextElement. The remove

method removes from the underlying Collection the last element that was returned by

next. The remove method may be called only once per call to next, and throws an

exception if this condition is violated. Note that Iterator.remove is the only safe way to

modify a collection during iteration; the behavior is unspecified if the underlying

collection is modified in any other way while the iteration is in progress. 

The following snippet shows you how to use an Iterator to filter a Collection, that is, to

traverse the collection, removing every element that does not satisfy some condition: 

static void filter(Collection c) {

   for (Iterator i = c.iterator(); i.hasNext(); )

       if (!cond(i.next()))

       i.remove();

}

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