Vector Classes

 

1. Vector class is present under the package 'util' (java.util.vector).

2.Vector class is same as ArrayList but vector methods are synchronized for safety purpose.

3. Vector is the only class other than ArrayList which provides random access to the data elements.

4. Vector class is used to create the vector array which is dynamic in nature & stores homogeneous as well as heterogeneous type of data.

5. There is no upper limit to store number of data values into vector array i.e. vector array is growable.

6. Vector cannot store basic data type directly. It only requires the data in the form of object numbers.

7. Vector array can be declared without specifying the size. A vector array without size can store unknown no of data elements that may vary in size.

Difference between Array and Vector

Advantages of Vector

1. Vector provides a way to store heterogeneous and homogeneous type of data in the form of object.

2. Vector can be used to store the data elements that may vary in size.

3. Vector class provides specialized methods for insertion, deletion, copy & other Manipulations.

Drawbacks of Vector

1. Vector cannot store basic data type directly.

2. Vector can only store the object type of data.

3. To store the basic data type in a vector, we require the conversion from basic data types to object numbers using wrapper classes.

Constructor of Vector class

1. Default Constructor: - To create a vector array width default size = 10, we must execute the default Constructor.

                     

                   Ex.. Vector V = new Vector ();

2. Parameterized Constructor width size as n: In the following constructor, vector array created with initial size n and once the size of vector array is full, the size will be incremented in multiples of n.

                   Ex.. Vector V = new Vector (n);

3. Parameterized Constructor (two parameter):

    

                   Ex. Vector V = new Vector (n, m);

Where n = initial size of vector array, m = increment of array as the capacity becomes full.

Non-static Methods of vector class: Create a vector array width default size.

                    Ex. Vector V = new Vector ();

1. v.addElement (data): It adds the data element at the end of vector.

2. v.insertElementAt (data, n)::The above method inserts the data element at nth position in a vector.

3. v.removeElementAt (n): :It remove data element from nth position of vector array

4. v1.copyInto (v2): It copies vector array v1 into vector array v2

5. v.size():It returns the size of vector array.

6. v.removeElementAll(): The method makes the vector array empty.

7. v.removeElement (data): It removes 1st occurrence of data element in the vector array.

8. v.firstElement(): It gives first element of vector array.

9. v.lastElement(): It gives last element of vector array.

10. v.elementAt (n) : The above method returns data element from nth position.

11. v.contains(data): It returns true if vector contains the data otherwise it returns false.

12. v1.equals(v2): It returns true if v1 is equal to v2 otherwise false.

1. java.util.Random: Random class generates a stream of pseudo-random numbers. To create a new random number generator, use one of the following methods: new Random(), new Random(long seed). The form new Random () initializes the generator to a value based on the current time. The form new Random(long seed) seeds the random number generator with a specific initial value; use this if an application requires a repeatable stream of pseudo-random numbers. To create a pseudo- random number, use one of the following functions:

Random(): Creates a new random number generator.

Random(long): Creates a new random number generator using a single long seed.

nextDouble(): Generates a pseudorandom uniformly distributed double value between 0.0 and 1.0.

nextFloat(): Generates a pseudorandom uniformly distributed float value between 0.0 and 1.0.

nextInt(): Generates a pseudorandom uniformally distributed int value. 

nextLong(): Generate a pseudorandom uniformally distributed long value.

2. The java.util.Date: A wrapper for a date. This class lets you manipulate dates in a system independent way. To print today's date use:

            Date d= new Date();     System.out.println("today = " + d);

To find out what day corresponds to a particular date:

            Date d = new Date(63, 0, 16); // January 16, 1963

            System.out.println("Day of the week: " + d.getDay());

     getMinutes() Returns the minute. 

     getMonth() Returns the month.

     getSeconds() Returns the second.

     getTime() Returns milliseconds.

     getYear() Returns the year after 1900.

     setDate(int) :Sets the date

     setDay(int) :Sets the day of the week. 

     setHours(int) :Sets the hours.

     setMinutes(int) :Sets the minutes.

     setMonth(int):Sets the month. 

     setSeconds(int) :Sets the seconds