Java class Vector

1
Java class Vector

• The Vector class implement a growable array of
  objects.
• User can use integer index to access items in a
  vector, like an array.
• A vector can expand or shrink as needed when add
  or delete items.
• Online document
• http//java.sun.com/j2se/1.4.2/docs/api/java/util/
  Vector.html

2
Fields of class Vector

• elementData
• Internal data array storing elements in the
  vector
• elementCount
• The number of elements stored in the vector. It
  is equal to the vectors size.
• capacityIncrement
• The amount by which the capacity of the vector is
  automatically incremented when it becomes full.

3
Define objects of Vector

• Before defining objects of Vector, import it.
• import java.util.Vector // import is like
  using namespace in C, C
• or
• import java.util.
• Define Vector objects, use different constructors
• Vector v1 new Vector()
• // v1 is empty. Its initial capacity is 10 and
  capacityIncrement is 0.
• Vector v2 new Vector(50)
• // v2 is empty. Its initial capacity is 50 and
  capacityIncrement is 0.
• Vector v3 new Vector (80, 5)
• // v3 is empty. Its initial capacity is 80 and
  capacityIncrement is 5.

4
Methods in Vector

• Add elements into a vector
• void add(int index, Object element)
• Add element at position index
•  boolean add(Object o)
• Append o at the end of the vector.

5
Methods in Vector

• Remove elements from a Vector
• boolean remove(Object obj)
• Remove the first occurrence of obj from the
  vector
• Return false if obj is not found.
• Object remove(int index)
• Remove element at location index and return
  it. 

6
Methods in Vector

• Search elements in an vector
• int indexOf(Object elem)
• Search for the first occurrence of elem and
  return its index.
• int indexOf(Object elem, int index)
• Searches for the first occurence of elem,
  beginning the search at index.
• Both return -1 if elem is not found.
• More
• int lastIndexOf(Object elem)
• int lastIndexOf(Object elem, int index)

7
Use methods in Vector

• Vector class provide lots of useful methods
• int size()
• Object set(int index, Object element)
• Object get(int index)
• void clear()
• // Much more
• Make good use them will make your coding much
  easier.
• For instance,
• // Output all elements in vector v1.
• System.out.println(v1.toString())