2/13/12

JDBC : Accessing Result Sets - Part I

This is my 3rd post on JDBC TUTORIAL. Today we will be learning about how to access the results that we get for a query using ResultSet. 

Whenever we execute a query to retrieve data from a table using a Java application, the output is stored in a ResultSet object in a tabular format. The ResultSet object maintains a cursor that helps us to move to and fro in the rows stored in the object and the cursor intially points before the first row.


2/1/12

Regular Expressions in Java

A regular expression is a kind of pattern that can be applied to text (String, in Java). Java provides the java.util.regex package for pattern matching with regular expressions. Java regular expressions are very similar to the Perl programming language and very easy to learn.

A regular expression either matches the text ( or a part of it) or it fails to match.
* If regular expression matches a part of text then we can find it out which one.
** If regular expression in complex, then we can easily find out which part of the regular expression matches with which part of the text.

1/27/12

Minimax Algorithm Tutorial

There are plenty of application in AI but games are the most important thing in today's world and nowadays every OS comes with two player games like chess, checkers etc. So there are algorithm that help to design these games. These algorithm not only just help in making games but they also help in making the life of the player(i.e. user) tough in the game-play. So Minimax Algorithm is one such kind of algorithm. 



1/26/12

Find the largest sum in an Array Problem

You are given an array of integers (both positive and negative). Find the continuous sequence with the largest sum. Return the sum.

 EXAMPLE

 input: {2, -8, 3, -2, 4, -10}
output: 5 [ eg, {3, -2, 4} ]
Answer  :
You might have identified that dynamic programming is appropriate for this problem. Let’s write down the recurrence:

 sum(i,j) = max_k sum(i,k) + sum(k+1, j)

 This will give an O(N^3) solution. A brute force summing of the sequences will give the same time.

 A simple linear algorithm will work by keep track of the current subsequence sum. If that sum ever drops below zero, that subsequence will not contribute to the subsequent maximal subsequence since it would reduce it by adding the negative sum.

 


public class SumArr {

    public static void main(String[] args) {
        int a[] = {6,-8, 3, -2, 4};
        int maxsum = 0;
        int sum = 0;
        for (int i = 0; i < a.length; i++) {
        sum += a[i];
        if (maxsum < sum) {
        maxsum = sum;
        } else if (sum < 0) {
        sum = 0;
        }
        }
        System.out.println(maxsum);
    }
}


1/16/12

Counting Sort Algorithm with Example

After a long interval of time I am writing a post on ALGORITHMS. After writing posts on Heap Sort, Merge Sort and Insertion Sort, I decided to write on Counting Sort.

Counting sort is an algorithm for sorting a collection of objects according to keys that are small integers; that is, it is an integer sorting algorithm. It is a linear time sorting algorithm used to sort items when they belong to a fixed and finite set. 

1/12/12

Advance I/O Streams in Java

A Stream is a flow of data from the source to a sink. Source and sink are also called input and output streams, respectively. 

 The I/O Streams are of two Kinds :
1. Byte Streams 
2. Character Streams

Normally the term stream refers to the byte stream and the terms  reader and writer refer to the character stream.