Sunday, June 29, 2014
How to sign data with digital signature ?
1. Form the message to be signed.
2. Generate a public-private key pair
3. Calculate hash of the message and encrypt it with sender's private key
4. Send the dugutally signed message with the signature along with the public key.
In this tutorial, we will be signing the data stored in a file. The file path will be taken as an input. The resulting output will be two file : a .dsa file containing the digital signature, and a .pubkey file containing the public key in encoded form.
Sunday, June 15, 2014
Below are the steps you must follow to implement watch service
1. Get the path of the folder - The first step is to get the Path object associated with the folder. This is done using Paths.get() method.
2. Get file system of the path - Next step is to get the FileSystem object associated with the Path object. This is done using getFileSystem() method.
3. Get watch service - Next you have to get WatchService from FileSystem object using newWatchService() method.
Monday, June 9, 2014
Similarly in the game that is developed here follows the rules - 1. Only one disk can be moved at a time. 2. Cannot place a larger disk on a smaller disk. The game her when starts will start with 4 initial disks. You will have to move all the disk to 3rd tower. You can use this game and ask people to complete and win the game of Tower of Hanoi. You also have a choice to select the number of disks you want to play with. So our main objective her is that we will actually not solve the Tower of Hanoi problem, rather use it as a game and ask players of the game to solve the problem.
Sunday, June 8, 2014
The code is written to support generics. This means that only one code has to be written for binary search tree(BST). You can insert anything in the tree but the objects must be comparable. Comparable objects here means that classes of those objects must extend java.lang.Comparable interface. The comments are also added to the code in Javadoc style
Thursday, June 5, 2014
In our first annotation we will just start with an empty annotation specifying only
import java.lang.annotation.*;
@Target(value={ElementType.FIELD})
@Retention(value=RetentionPolicy.RUNTIME)
public @interface Author {
}
In the next example you will see that when there is only one value for an annotation then we can omit the name as well as braces{} indicating arrays. The above sample is re-written asimport java.lang.annotation.*;
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Author {
}
In our next example you will see how to mention the target type when it is more than one say FIELD and METHOD.import java.lang.annotation.*;
@Target({ElementType.FIELD, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Author {
}
In our next example we will deal with annotation which has annotation type elements. It looks almost like methods. We will also show you how to use this annotation in a class.import java.lang.annotation.*;
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Author {
String name();
}
class MyClass {
@Author(name="Nirupam")
int i = 10;
}
In our next and last example of today, we will show you how to mention default values of annotation type elements. It is done using keyword default . If a default value is mentioned, then you can omit adding your own value. But it does not mean that you cannot add your own value, of course you can do it.import java.lang.annotation.*;
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Author {
String name() default "Nirupam";
}
class MyClass {
@Author
int i = 10;
}
In our next and last part we will deal with creating and using advanced annotation. Till then keep coding and keep reading our articles.
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