Find the String length without using the String API of Java

                                   Generally, String is collection of Characters.String are immutable objects in Java. String is playing vital role in Java programming language. Java main() method parameter is also String array and Java is taking defaultly String. If we want to know the length of the String in java by using String API method length().But my question is how to find the length of the String without using String API of Java. Is it possible to find the String length without String API? Yes,it is possible to find String length without String API.

                                  By using File concept we can find the length of the String. By storing the each character of the String into the file and parallelly counting the characters. See the below example

package com.rrvtechdiamond;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class LengthOfString {

public static void main(String[] args) throws IOException {

          String nameOfBlog = "RRV TECH DIAMOND";
          
 File file = new File("G:/rrvtechdiamond.txt");//creating file object
 
 file.createNewFile();// creating file 
 
 
 FileWriter fileWriter = new FileWriter(file);
 
 fileWriter.write(nameOfBlog);//By using the write method write String to file
 
 fileWriter.close();//close the file
 
 FileReader fileReader = new FileReader(file);//create FileReader object
          
 int characterValue = 0, count = 0;
 
 while((characterValue = fileReader.read()) != -1){
 count++;
 }
 fileReader.close();//close fileReader
 
 System.out.println("length of the String is: "+count);
 
 
}

Output :

length of the String is: 16

Rename the name of the file with current system date by using java program

                      File is using to store the data permanently on disk in computer. We give names to individual files. Creating file, saving the file and renaming the file on GUI system very easy but programmatically we write some code and today our topic is this one. See the below program for the answer.   


import java.io.File;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;

public class DateAsFileName {
public static void main(String[] args) throws IOException {
         // create file object
         File file=new File("G:/text.txt");
         //create DateFormat object 
        file.createNewFile();
         
         //create calendar class object
         Calendar calendar = Calendar.getInstance();
         Date ss = calendar.getTime();
         int day = calendar.get(calendar.DAY_OF_MONTH); 
         int month = calendar.get(calendar.MONTH);
         int year = calendar.get(calendar.YEAR);
         String s="G:/"+day+"-"+month+"-"+year+".txt";
        file.renameTo(new File(s));
}

}
        

Find Number of days between two given dates in Javascript

My question is Find number of days between the two given dates by using javascript. See below code, copy and paste the code into your html page in head tag.

<script>
function   DiffInDays(startDate, endDate){
      startDate = new Date(startDate);
      endDate = new Date(endDate);
      if(endtDate.getTime() > startDate.getTime())
      {
             var diffDays = endDate.getDate() - startDate.getDate();
             alert("Difference in Days :"+diffDays/86400000);// MilliSeconds for one day is 1000*60*60*24
       }
       else  if(endtDate.getTime() == startDate.getTime()){
             alert("StartDate and endDate are equal");
       }
       
}
</script>

Digit available number of times in given range

package com.rrvtechdiamond;

import java.util.Scanner;

class NumberOfDigits

{

public static void main (String[] args) throws java.lang.Exception

{

Scanner scanner=new Scanner(System.in);

                System.out.println("Enter up to which range you want: "); 

int numberRange=scanner.nextInt();

System.out.println("Enter which digit you want");

int digit=scanner.nextInt();

int count=0;/*count for counting number of digit available within                     given range*/

//for loop start with 0 up to given range

for(int i=0;i<numberRange;i++){

int innerCount=0;/*this count for given digit is available or                                           not if given digit is find more than one time we                                                will print that i value*/

int j=i;

while(j>0)

{

int temp=j%10;

if(temp==digit)

{

innerCount++;

count++;

}

j=j/10;

}

if(innerCount>0){

System.out.println(i);

}

}

System.out.println("You enter digit comes in "+count+" times");

}

}

OUTPUT:

Enter up to which range you want:

100

Enter which digit you want

8

8

18

28

38

48

58

68

78

80

81

82

83

84

85

86

87

88

89

98

You enter digit comes in 20 times

About JSON

What is XML?

                 XML(Extensible markup language) is a data-interchange format.In this format values is surrounded  with start and end tags.Xml is derived from SGML(Standard Generalized Markup Language). This format is used for to sending data from one computer to remote computer in a network.It is easy to read and write for humans. For parsing xml data, we use xml parsers. This parsers verify that particular xml file well-formed and valid based on respective DTD(Document Type Definition) file.

Disadvantages with XML:

1.It doesn't support data types.

2.Its XML parser takes more time to process the XML file.

3.File size is limited.

4. For storing xml data to object and vice-versa is high cost process.

5.This format is not good for sending data from client to server or vice-versa.

    To over come above problems JSon is used.

What is JSON ?

             JSON(JavaScript Object Notation) is a lightweight data-interchange format.It is easy for humans to read and write and easy for machine to parse and generate.This JSon is developed from JavaScript programming language,standard ECMA-262 Edition December 1999.JSON is a text format that is completely language independent.

How many ways we can write JSON ?

We can built JSon in two ways.

1.Collection of name/value pairs.In various languages,this is realized as an object, record, struct, dictionary, hash-table, key-list, or associative array.

2. An ordered list of values.In most  languages this is relialized as an array,vector,list or sequence.

This are universal data structures.Virtually all modern programming languages support them in one form of another. It makes sense that a data format that is interchangeable with programming languages also be based on this structure.

Advantages of JSon:

1.This format is supported by every browser and parser is parsing data very fastly.

2.To send data from client to server or vice-verse  JSON is better than XML.

3.It store data in form of name /value pairs.

4.JSon is used for consumption of data in web applications from webservices for its size and ease of use.

5.JSon is Data-oriented,so so JSon is easily mapped with object-oriented systems.

6. A browser JSon is faster for serializing and de-serializing.

Example :

I have xml file file like below

<order>

<itemno>10</itemno>

<itemName>LUX</itemName>

<qty>2</qty>

</order>

Now i am converting XML to JSon

Syntax of JSON file:

{

-----

-----

-----

}

Example 1:

json1.json:

{//start

{

    "order": {

        "itemno": "10",

        "itemName": "LUX",

        "qty": "10" (Donot give  coma (,)for last field)

}

}//end

The above format is Object format and below format is Array format

Example 2:

json2.json:

{

"order": [

        {

            "itemno": "10",

            "itemName": "LUX",

            "qty": "10" (Donot give  coma (,)for last field)

        }   ]

]

}

Example 2:

{

    "array": [  1, 2, 3 ],

    "boolean": true,

    "null": null,

    "number": 123,

    "object": {

        "a": "b",

        "c": "d",

        "e": "f"

    },

    "string": "Hello World"

}

If you want validate your JSON, copy  and paste your json in this site

www.jsoneditoronline.org

http://jsonlint.com/

How to delete elements from Array in java

Array is collection of homogenous fixed size number of elements.If we want to create array object in our program, we should know the size of the array.It is a big problem to the programmers and clients.And once we create an array, cannot change its size and cannot delete elements from array.If you want to delete any element from array,you should create one more array and copy that array elements to this array except which elements you want to delete by using for loop. In java array is object but we donot have method like add,delete thats why collections are introduced in 1.2 version. To reducing burden of developers Apache giving one jar(Download) file. By using this array we can add or delete elements from array.See below snippet

package com.rrv;

import org.apache.commons.lang.ArrayUtils;

 public class ArrayElementDelete

{

   public static void main(String[] args){

      //create array object

     int[] naturalNumber = {1,2,3,6,4,7,6,8,9};

     System.out.println (" Array elements:  "+Arrays.toString(naturalNumber));

     

     //now you can delete element from array

    naturalNumbe = ArrayUitls.remove(naturalNumbers,5); //deleting index 5

   

     // After deleting element from array print the array elements

     System.out.println (" Array elements:  "+Arrays.toString(naturalNumber));

  }

}

Output:

Array elements: 1 2 3 6 4 7 6 8 9

Array elements: 1 2 3 6 4 6 8 9

  

Octal to Decimal in Java

This program is written for to convert octal  number to decimal number programmatically. It is a important interview question and this program as logic to convert octal to decimal.

                                First we find the given number is octal or not. Then we will write logic for decimal number from octal. Observe below logic how to write logic to convert octal to decimal.

package com.rrv;
import java.math.*;
import java.util.Scanner;
//class for converting Octal to Decimal
class OctalToDecimal
{
 //main method
  public static void main(String[] args)
    {  
      //declare boolean type variable for to check given number is octal or not 
       boolean is_Octal=false;
       //create scanner object for taking values from user
       Scanner scanner=new Scanner(System.in);
       System.out.println("Enter Octal Number ");
       int octalNum=scanner.nextInt();
      //call isOctal() method for finding given number is octal or not
       is_Octal= isOctal(octalNum);
      //check given number is octal or not,if true call octalToDecimal() method else print message to console
       if (is_Octal==true){
         octalToDecimal(octalNum);
       }
      else
       {
         System.out.println("Entered Number is not octal number. Please enter Octal number");
       }
    }
// method for finding given number is octal or not
  public static boolean isOctal(int octalNum)
    { 
      //declare remainder variable for to store remainder value
        int remain=0;
     //if octal number is > zero then enter into while loop
        while(octalNum>0)
          {
              remain=octalNum%10;
               if(remain<8)
                {
                   octalNum=octalNum/10;
                 }
              else{
                  return false;
                }
          }
        return true;
     }
//method for convert into decimal
public static void octalToDecimal(int octalNum)
{
   int inputNumber=octalNum;
   int remain=0;
   int count=0;
   int decimal=0;
   while(inputNumber>0)
    {
       remain=inputNumber%10;
       //first find power value of 8 with count and multiply with remainder then add to decimal variable
       decimal=(int) (decimal+remain*Math.pow(8,count));
       count++;
      inputNumber=inputNumber/10;
    }
    System.out.println("The Decimal number for "+octalNum+"  octal is: "+decimal);
  }
}

OutPut:

Enter Octal Number 
173

The Decimal number for 173  octal is: 123

Enter Octal Number 
189

Entered Number is not octal number. Please enter Octal number