Lecture 13: StringTokenizer and Vector class in Java смотреть онлайн

StringTokenizer and Vector class in Java :
StringTokenizer :




Vector:
• Once we declare array with some capacity or size we cannot change it easily.
• The easiest way in java to deal with this common situation is to use another Java class that works much like array is vector.
• Vector implements a dynamic array.
• Vector class contains following constructors:
Vector ()
Vector (int size)
Vector(int size, int increment)
• First constructor creates default vector, which has an initial size of 10.
• Second constructor creates a vector whose initial capacity is specified by size.
• Third type of constructor creates a vector whose initial capacity is specified by size, and whose increment is specified by increment.
• All vector start with initial capacity. After this initial capacity is reached, next time that you attempt to store an object in vector, vector automatically allocates space for that object plus extra room for additional objects depending upon capacity of vector.
• Vector class contained in java.util package. This class can be used to create a generic dynamic array known as vector that can hold objects of any type and any number.
• The objects do not have to be homogenous. Arrays can be easily implemented as vectors.
• Vectors are created like arrays as follows :
Vector intVect = new Vector(); // declaring without size.
Vector list = new Vector(3); // declaring with size.
• Vector possess a number of advantages over arrays:
1. It is convenient to use vectors to store objects.
2. A vector can be used to store a list of objects that may vary in size.
3. We can add or delete objects from list as and when required.
• A major constraints using vectors is that we cannot directly store simple data in a vector, we can only store objects.
• Therefore, we need to convert simple type to objects. This can be done using the wrapper classes.
• Vector class supports a number of methods that can be used to manipulate the vectors that is created.