Sort Java Vector in descending order using comparator

Sort Java Vector in descending order using comparator example his java example shows how to sort elements of Java Vector in descending order using comparator and reverseOrder method of Collections class.

mport java.util.Vector;
mport java.util.Collections;
mport java.util.Comparator;
 
public class SortVectorInDescendingOrderExample {
 
  public static void main(String[] args) {
   
    //create a Vector object
    Vector v = new Vector();
   
    //Add elements to Vector
    v.add("1");
    v.add("2");
    v.add("3");
    v.add("4");
    v.add("5");
   
    /*
      To get comparator that imposes reverse order on a Collection use
      static Comparator reverseOrder() method of Collections class
    */
   
    Comparator comparator = Collections.reverseOrder();
   
    System.out.println("Before sorting Vector in descending order : " + v);
   
    /*
      To sort an Vector using comparator use,
      static void sort(List list, Comparator c) method of Collections class.
    */
   
    Collections.sort(v,comparator);
    System.out.println("After sorting Vector in descending order : " + v);
   
  }
}

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Demonstrate various Vector operations

Here is a Java Program to Demonstrate various Vector operations.

import java.util.*;

class VectorDemo {
  public static void main(String args[]) {

    // initial size is 3, increment is 2
    Vector v = new Vector(3, 2);

    System.out.println("Initial size: " + v.size());
    System.out.println("Initial capacity: " +
                       v.capacity());

    v.addElement(new Integer(1));
    v.addElement(new Integer(2));
    v.addElement(new Integer(3));
    v.addElement(new Integer(4));

    System.out.println("Capacity after four additions: " +
                       v.capacity());
    v.addElement(new Double(5.45));
    System.out.println("Current capacity: " +
                       v.capacity());
    v.addElement(new Double(6.08));
    v.addElement(new Integer(7));

    System.out.println("Current capacity: " +
                       v.capacity());
    v.addElement(new Float(9.4));
    v.addElement(new Integer(10));

    System.out.println("Current capacity: " +
                       v.capacity());
    v.addElement(new Integer(11));
    v.addElement(new Integer(12));


    System.out.println("First element: " +
                       (Integer)v.firstElement());
    System.out.println("Last element: " +
                       (Integer)v.lastElement());

    if(v.contains(new Integer(3)))
      System.out.println("Vector contains 3.");

    // enumerate the elements in the vector.
    Enumeration vEnum = v.elements();

    System.out.println("\nElements in vector:");
    while(vEnum.hasMoreElements())
      System.out.print(vEnum.nextElement() + " ");
    System.out.println();
  }
}

Output of Above Java Program
Initial size: 0
Initial capacity: 3
Capacity after four additions: 5
Current capacity: 5
Current capacity: 7
Current capacity: 9
First element: 1
Last element: 12
Vector contains 3.

Elements in vector:
1 2 3 4 5.45 6.08 7 9.4 10 11 12

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Java Program to Store a deck of 52 cards in a Linked List

Write a program to store a deck of 52 cards in a linked list in random sequence using a Random class object. You can represent a card as a two-character string "1C" for the ace of clubs, "JD" for the jack of diamonds, and so on. Output the cards from the linked list as four hands of 13 cards.

import java.util.Vector;
import java.util.LinkedList;
import java.util.Random;
import java.util.ListIterator;

public class DealCards {
  public static void main(String[] args) {
    String[] suits = {"C", "D", "H", "S"};
    String[] cardValues = { "1","2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"};

    int cardsInDeck = 52;
    Vector<String> deck = new Vector<String>(cardsInDeck);
    LinkedList<String> shuffledDeck = new LinkedList<String>();
    Random chooser = new Random();                                     // Card chooser

    // Load the deck
    for(String suit : suits) {
      for(String cardValue : cardValues) {
        deck.add(cardValue + suit);
      }
  }

    // Select cards at random from the deck to transfer to shuffled deck
    int selection = 0;                                                 // Selected card index
    for(int i = 0 ; i < cardsInDeck ; ++i) {
      selection = chooser.nextInt(deck.size());
      shuffledDeck.add(deck.remove(selection));
    }

    // Deal the cards from the shuffled deck into four hands
    StringBuffer[] hands = { new StringBuffer("Hand 1:"), new StringBuffer("Hand 2:"),
                             new StringBuffer("Hand 3:"), new StringBuffer("Hand 4:")};
    ListIterator<String> cards = shuffledDeck.listIterator();

    while(cards.hasNext()) {
      for(StringBuffer hand : hands) {
        hand.append(' ').append(cards.next());
      }
    }

    // Display the hands
    for(StringBuffer hand : hands) {
      System.out.println(hand);
    }
  }
}

Output of Above Java Program

Hand 1: 3D KS 8C 9S 10D 4D 5C JC 8D 1C 5S 10C 7C
Hand 2: 5D 1H 6H 7H 5H 3H KH 6D 10S QC 9D 7S 3C
Hand 3: 1D 9C QH 2S QD 2C 6C JH 8H KD JD 4H 7D
Hand 4: 9H 1S 4C 3S 10H KC 2H 4S QS 8S 2D 6S JS

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Program to Calculate Prime Numbers using Vector

Implement a version of the program to calculate prime numbers to use a Vector<> object instead of an array to store the primes.

import java.util.Vector;

public class MorePrimes {
  public static void main(String[] args) {
    Vector<Long> primes = new Vector<Long>();                          // Vector to store primes
    int primesRequired = 20;                                           // Number of primes required

    primes.add(new Long(2L));                                          // Seed the first prime
    primes.add(new Long(3L));                                          // and the second
    long number = 5L;                                                  // Next integer to be tested
    long divisor = 0L;                                                 // Stores current trial divisor

    outer:
    for( ; primes.size() < primesRequired; number += 2) {
      // The maximum divisor we need to try is square root of number
      long limit = (long)Math.ceil(Math.sqrt((double)number));

      // Divide by all the primes we have up to limit
      for(int i = 1; i < primes.size() && (divisor = primes.elementAt(i)) <= limit; ++i) {
        if(number%divisor == 0) {                                      // Is it an exact divisor?
          continue outer;                                              // Yes, try the next number
        }
      }
      primes.add(number);                                              // We got one!
    }
    // Output all the primes six to a line
    int count = 0;
    for(Long prime : primes) {
      System.out.printf("%15d", prime);
      if(++count%6 == 0) {
        System.out.println();
      }
    }
  }
}

Output of Above Java Program

              2              3              5              7             11             13
             17             19             23             29             31             37
             41             43             47             53             59             61
             67             71

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