A Complete article on String class in Java

A Complete article on String class in Java

String var = new String("Google interview questions");

There is a high chance you came across the questions about String in most of the interviews.

What is a String?

We can say a string as a sequence of characters.

How a string implemented?

The string is implemented as an array of bytes that stores the character using a certain specific character encoding ( Say for example CP1144)

How this Character Encoding works?

Java uses UTF-16 character encoding internally to store a string.

Java supports a wide range of encoding.

Sample Java code :-

String crackInterview = new String("Facebook interview questions");

byte[]  elonmask=  crackInterview.getBytes();

byte[]  uber=  crackInterview.getBytes("CP1044");

will return different results.

How to create a String in Java?

There are two ways to create a string in java. One by String literal and other by new keyword.

String var = "Amazon interview questions"; ( using literals )

String var = new String("Microsoft interview questions"); ( using new operator)

There will be some differences in creating in these ways, right?

yes, while using new operator a string will be created in the string pool as well as in heap memory. 

on the other hand while using literals string will be created on spring pool

Then what is a string pool? why java using a String pool?

Simply a pool of string in heap memory.

String pool is an implementation of String interning concept, developed on flyweight design pattern. 

we can use the intern() method to put back the string created using a new operator to string pool.

Since the value of the string object does not change, we called String is immutable.

Why we kept the string in a pool?

Security and Immutable

What is the flyweight design pattern?

A creational software design pattern.

Minimizing memory usage by share similar data.

How String becomes mutable?

To become string a mutale one we need to implement either StringBuilder or StringBuffer class


@author : Konzernites

Budget Preparation monthly estimation of budget java source code cfed

import java.io.IOException;

import javax.swing.JOptionPane;

/**

 * 

 */

/**

 * @author vipin

 *

 */

public class MainClass {

/**

* @param args

*/

public static void main(String[] args) {

    ReadExcel test = new ReadExcel();

   test.setInputFile("BUDGET.xls");

  // test.setInputFile("BUDGET.xls");

    try {

test.read();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

JOptionPane.showMessageDialog(null, "Err"+e.getMessage());

}

}

}

import java.io.File;

import java.io.IOException;

import java.util.HashMap;

import java.util.Map;

import java.util.Vector;

import javax.swing.JOptionPane;

import jxl.Cell;

import jxl.CellType;

import jxl.Sheet;

import jxl.Workbook;

import jxl.read.biff.BiffException;

import jxl.write.WriteException;

/**

 * 

 * @author cfed

 *

 */

public class ReadExcel {

  private String inputFile = null;

  private BudgetCreator budgetCreator = null;

  

  //private Vector<Vector> array =null;

  

  private Map<Integer,Double> lastFinYrRetail = null;

  private Map<Integer,Double> lastFinYrSbdy = null;

  private Map<Integer,Double> newFinYrRetail = null;

  private Map<Integer,Double> newFinYrSbdy = null;

  private Map<Integer,Double> budgetData = null;

  

  private int lstYrsRFirmCode = 0;

  private double lstYrsRValue = 0;

 

  private int lstYrsSFirmCode = 0;

  private double lstYrsSValue = 0;

  

  private int newYrsRFirmCode = 0;

  private double newYrsRValue = 0;

  private int newYrsSFirmCode = 0;

  private double newYrsSValue = 0;

  

  private int budgetFirmCode = 0;

  private double budgetValue = 0;

  public void setInputFile(String inputFile) {

    this.inputFile = inputFile;

  }

  public void read() throws IOException  {

  budgetCreator = new BudgetCreator();

// array = new Vector<Vector>();

  lastFinYrRetail = new HashMap<Integer, Double>();

  lastFinYrSbdy= new HashMap<Integer, Double>();

  newFinYrRetail = new HashMap<Integer, Double>();

  newFinYrSbdy= new HashMap<Integer, Double>();

  budgetData= new HashMap<Integer, Double>();

    File inputWorkbook = new File(inputFile);

    Workbook w;

    try {

      w = Workbook.getWorkbook(inputWorkbook);

      Sheet sheet = w.getSheet("Sheet1");

      

     int rowCount = sheet.getRows();

     int colCount = 10;

      

      for(int row=0; row<rowCount; row++){

      

      for(int col=0;col<colCount;col++){

      

      Cell cell = sheet.getCell(col, row);

      CellType type = cell.getType();

      String value = cell.getContents();

      switch (col) {

case 0:

lstYrsRFirmCode = budgetCreator.getNameFirmCode(value);

break;

case 1:

if(lstYrsRFirmCode>0&&(type==CellType.NUMBER)){

lstYrsRValue = Double.parseDouble(value);

    lastFinYrRetail.put(lstYrsRFirmCode, lstYrsRValue/100000);  // first retails input

}

break;

case 2:

lstYrsSFirmCode = budgetCreator.getNameFirmCode(value);

break;

case 3:

if(lstYrsSFirmCode>0&&(type==CellType.NUMBER)){

lstYrsSValue = Double.parseDouble(value);

    lastFinYrSbdy.put(lstYrsSFirmCode, lstYrsSValue/100000); // first sbdy input

}

break;

case 4:

newYrsRFirmCode = budgetCreator.getNameFirmCode(value);

break;

case 5:

if(newYrsRFirmCode>0&&(type==CellType.NUMBER)){

newYrsRValue = Double.parseDouble(value);

    newFinYrRetail.put(newYrsRFirmCode, newYrsRValue/100000); // new retail input

}

break;

case 6:

newYrsSFirmCode = budgetCreator.getNameFirmCode(value);

break;

case 7:

if(newYrsSFirmCode>0&&(type==CellType.NUMBER)){

newYrsSValue = Double.parseDouble(value);

    newFinYrSbdy.put(newYrsSFirmCode, newYrsSValue/100000); // new sbdy input

}

break;

case 8:

budgetFirmCode = budgetCreator.getNameFirmCode(value);

break;

case 9:

if((budgetFirmCode>0)&&(type==CellType.NUMBER)){  //add recently

budgetValue = Double.parseDouble(value);

    budgetData.put(budgetFirmCode, budgetValue); // budget value

}

break;

default:

break;

}

      

    }

   

      

      }

      

      Vector<Vector> array =budgetCreator.calculateBudget(lastFinYrRetail,lastFinYrSbdy,newFinYrRetail,newFinYrSbdy,budgetData);

      WriteExcel test = new WriteExcel();

         test.setOutputFile("BUDGET_REPORT.xls",array);

    //test.setOutputFile("BUDGET_REPORT.xls",array);

          test.write();

          JOptionPane.showMessageDialog(null, "Excel file : BUDGET_REPORT created !!! ");

          

    } catch (BiffException e) {

      e.printStackTrace();

      JOptionPane.showMessageDialog(null, "Err"+e.getMessage());

    } catch (WriteException e) {

// TODO Auto-generated catch block

e.printStackTrace();

JOptionPane.showMessageDialog(null, "Err"+e.getMessage());

}catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

JOptionPane.showMessageDialog(null, "Err"+e.getMessage());

}

  }

} 

import java.util.HashMap;

import java.util.Map;

public class UnitsMap {

private Map<Integer,String> unitMap = null;

public UnitsMap(){

unitMap = new HashMap<Integer, String>();

//unitMap.put(287, "GROCERY SECTION MUTHALAKULM( 0287)");

}

public Map<Integer, String> getUnitMap() {

unitMap.put(287,"GROCERY SECTION MUTHALAKULM( 0287)");

unitMap.put(2002,"LITTLE TRIVENI  STORE  KOODARANJI( 2002)");

unitMap.put(2003,"LITTLE TRIVENI STORE KODANCHERY( 2003)");

unitMap.put(2750,"LITTLE TRIVENI STORE KOODATHAI( 2750)");

unitMap.put(2001,"LITTLE TRIVENI STORE KOOLIMADU( 2001)");

unitMap.put(2649,"LITTLE TRIVENI STORE PANAMARAM( 2649)");

unitMap.put(2650,"LITTLE TRIVENI STORE VAALAD( 2650)");

unitMap.put(304,"LITTLE TRIVENI SUPER STORE  K P K( 0304)");

unitMap.put(327,"LITTLE TRIVENI SUPER STORE CHERUVAD( 0327)");

unitMap.put(2538,"LITTLE TRIVENI SUPER STORE KARASSERY( 2538)");

unitMap.put(410,"LITTLE TRIVENI SUPER STORE KODUVALL( 0410)");

unitMap.put(2514,"LITTLE TRIVENI SUPER STORE MANASSERY( 2514)");

unitMap.put(619,"MINI TRIVENI STORE KULAGARA( 0619)");

unitMap.put(2648,"MINI TRIVENI STORE PANNIMUKKU( 2648)");

unitMap.put(2540,"MOBILE TRIVENI BALUSSERY( 2540)");

unitMap.put(2541,"MOBILE TRIVENI BEYPORE( 2541)");

unitMap.put(2507,"MOBILE TRIVENI CALICUT NORTH( 2507)");

unitMap.put(1893,"MOBILE TRIVENI CALICUT SOUTH( 1893)");

unitMap.put(2505,"MOBILE TRIVENI KALPETTA( 2505)");

unitMap.put(2544,"MOBILE TRIVENI KODUVALLI( 2544)");

unitMap.put(2635,"MOBILE TRIVENI KOYILANDY( 2635)");

unitMap.put(2543,"MOBILE TRIVENI KUNNAMANGALAM( 2543)");

unitMap.put(2633,"MOBILE TRIVENI KUTTIADY( 2633)");

unitMap.put(1895,"MOBILE TRIVENI MANANTHAVADY( 1895)");

unitMap.put(2542,"MOBILE TRIVENI NADAPURAM( 2542)");

unitMap.put(2632,"MOBILE TRIVENI PERAMBRA( 2632)");

unitMap.put(1892,"MOBILE TRIVENI STORE ELATHOOR( 1892)");

unitMap.put(1894,"MOBILE TRIVENI SULTHANBATHERI( 1894)");

unitMap.put(2508,"MOBILE TRIVENI THIRUVAMPADI( 2508)");

unitMap.put(2634,"MOBILE TRIVENI VATAKARA( 2634)");

unitMap.put(257,"TRIVENI DEPARTMENT COSMETICS MUTHAL( 0257)");

unitMap.put(259,"TRIVENI GIFT LAND MUTHALAKULAM( 0259)");

unitMap.put(340,"TRIVENI GODOWN  VATAKARA( 0340)");

unitMap.put(33,"TRIVENI GODOWN GROCERY( 0033)");

unitMap.put(261,"TRIVENI SUPER MARKET  VATAKARA( 0261)");

unitMap.put(430,"TRIVENI SUPER MARKET BALUSSERY( 0430)");

unitMap.put(2977,"TRIVENI SUPER MARKET EASTHILL( 2977)");

unitMap.put(325,"TRIVENI SUPER MARKET FEROKE( 0325)");

unitMap.put(2804,"TRIVENI SUPER MARKET KADIYANGAD( 2804)");

unitMap.put(422,"TRIVENI SUPER MARKET KAKKATTIL( 0422)");

unitMap.put(431,"TRIVENI SUPER MARKET KALPATTA( 0431)");

unitMap.put(260,"TRIVENI SUPER MARKET KOYILAN( 0260)");

unitMap.put(450,"TRIVENI SUPER MARKET KUNNAMANGALAM( 0450)");

unitMap.put(266,"TRIVENI SUPER MARKET MANANTHAVADY( 0266)");

unitMap.put(414,"TRIVENI SUPER MARKET MEENANGADY( 0414)");

unitMap.put(258,"TRIVENI SUPER MARKET NADAKKAVU( 0258)");

unitMap.put(432,"TRIVENI SUPER MARKET NADAPURAM( 0432)");

unitMap.put(379,"TRIVENI SUPER MARKET PAROPADI( 0379)");

unitMap.put(328,"TRIVENI SUPER MARKET PERAMBRA( 0328)");

unitMap.put(263,"TRIVENI SUPER MARKET THAMARASSERY( 0263)");

unitMap.put(3001,"TRIVENI GODOWN KARASSERY(3001)");

return unitMap;

}

public void setUnitMap(Map<Integer, String> unitMap) {

this.unitMap = unitMap;

}

}

import java.io.File;

import java.io.IOException;

import java.util.Locale;

import java.util.Vector;

import jxl.CellView;

import jxl.Workbook;

import jxl.WorkbookSettings;

import jxl.format.UnderlineStyle;

import jxl.write.Formula;

import jxl.write.Label;

import jxl.write.Number;

import jxl.write.WritableCellFormat;

import jxl.write.WritableFont;

import jxl.write.WritableSheet;

import jxl.write.WritableWorkbook;

import jxl.write.WriteException;

import jxl.write.biff.RowsExceededException;

public class WriteExcel {

  private WritableCellFormat timesBoldUnderline;

  private WritableCellFormat times;

  private String inputFile;

  private Vector<Vector> array = null;

  public void setOutputFile(String inputFile) {

  this.inputFile = inputFile;

  }

  public void setOutputFile(String inputFile, Vector<Vector> array) {

  this.inputFile = inputFile;

  this.array = array;

}

  

  public void write() throws IOException, WriteException {

    File file = new File(inputFile);

    WorkbookSettings wbSettings = new WorkbookSettings();

    wbSettings.setLocale(new Locale("en", "EN"));

    WritableWorkbook workbook = Workbook.createWorkbook(file, wbSettings);

    workbook.createSheet("Report", 0);

    WritableSheet excelSheet = workbook.getSheet("Report");

    createLabel(excelSheet);

    createContent(excelSheet);

    workbook.write();

    workbook.close();

  }

  private void createLabel(WritableSheet sheet)

      throws WriteException {

    // Lets create a times font

    WritableFont times10pt = new WritableFont(WritableFont.TIMES, 10);

    // Define the cell format

    times = new WritableCellFormat(times10pt);

    // Lets automatically wrap the cells

    times.setWrap(true);

    // Create create a bold font with unterlines

    WritableFont times10ptBoldUnderline = new WritableFont(WritableFont.TIMES, 10, WritableFont.BOLD, false,

        UnderlineStyle.SINGLE);

    timesBoldUnderline = new WritableCellFormat(times10ptBoldUnderline);

    // Lets automatically wrap the cells

    timesBoldUnderline.setWrap(true);

    CellView cv = new CellView();

    cv.setFormat(times);

    cv.setFormat(timesBoldUnderline);

    cv.setAutosize(false);

    // Write a few headers

    addCaption(sheet, 0, 0, "SL No");

    addCaption(sheet, 1, 0, "Branch Name");

    addCaption(sheet, 2, 0, "Retail");

    addCaption(sheet, 3, 0, "Sbdy");

    addCaption(sheet, 4, 0, "Retail");

    addCaption(sheet, 5, 0, "Sbdy");

    addCaption(sheet, 6, 0, "Variation");

    addCaption(sheet, 7, 0, "Budget");

    addCaption(sheet, 8, 0, "Comparison");

    

  }

  private void createContent(WritableSheet sheet) throws WriteException,

      RowsExceededException {

  

  int size = array.size();

  sheet.setColumnView(1, 50);

      for(int row = 0; row < size; row ++){

  sheet.setRowView(row, 400);

  Vector val = array.get(row);

  for(int col =0; col<9;col++){

  addValues(sheet,col, row, val.get(col));

  }

}

  

  

  }

  private void addCaption(WritableSheet sheet, int column, int row, String s)

      throws RowsExceededException, WriteException {

    Label label;

    label = new Label(column, row, s, timesBoldUnderline);

    sheet.addCell(label);

  }

  private void addNumber(WritableSheet sheet, int column, int row,

      Integer integer ) throws WriteException, RowsExceededException {

 

    Number number;

    number = new Number(column, row, integer, times);

    sheet.addCell(number);

    

  }

  

  private void addValues(WritableSheet sheet, int column, int row, Object obj)

      throws WriteException, RowsExceededException {

    Label label;

    label = new Label(column, row, obj.toString(), times);

    sheet.addCell(label);

  }

  private void addLabel(WritableSheet sheet, int column, int row, String s)

      throws WriteException, RowsExceededException {

    Label label;

    label = new Label(column, row, s, times);

    sheet.addCell(label);

  }

} 

/**

 * Budget Creator

 */

import java.text.DecimalFormat;

import java.util.Map;

import java.util.Vector;

/**

 * Consumerfed kozhikode region

 */

/**

 * @author shimjith

 *

 */

public class BudgetCreator {

private UnitsMap unitMap = null;

private Vector<Vector> array = null; //output array

DecimalFormat decimalFormat = null;

public BudgetCreator(){

}

public int getNameFirmCode(String value) {

int firmCode = 0;

String str = value;

if(str.contains("(")&& str.contains(")")){

int startIndex = str.indexOf("(");

int endIndex = str.indexOf(")");

//System.out.println(true);

//System.out.println(startIndex + "--" +endIndex);

String sub = str.substring(startIndex+1, endIndex).trim();

sub = sub.trim();

//System.out.println(sub);

firmCode = Integer.parseInt(sub);

//System.out.println(" firmcode :"+firmCode);

}

return firmCode;

}

public void viewData(Map<Integer, Double> budgetData) {

// TODO Auto-generated method stub

System.out.println(" ------- Report -----------");

System.out.println(budgetData.size());

System.out.println(budgetData);

}

public Vector<Vector> calculateBudget(Map<Integer, Double> lastFinYrRetail,

Map<Integer, Double> lastFinYrSbdy,

Map<Integer, Double> newFinYrRetail,

Map<Integer, Double> newFinYrSbdy, Map<Integer, Double> budgetData) {

// TODO Auto-generated method stub

unitMap = new UnitsMap();

array = new Vector<Vector>();

Vector heading = new Vector();

heading.add("SLNO");

heading.add("BRANCH NAME");

heading.add("RETAIL");

heading.add("SBDY");

heading.add("RETAIL");

heading.add("SBDY");

heading.add("VARIATION");

heading.add("BUDGET");

heading.add("COMPARISON");

array.add(heading);

decimalFormat = new DecimalFormat("0.00");

Map map = unitMap.getUnitMap();

Vector data = null;

int serialNo = 1;

Double oldRetailTotal = 0.00;

Double oldSbdyTotal = 0.00;

Double newRetailTotal = 0.00;

Double newSbdyTotal = 0.00;

Double variationTotal = 0.00;

Double budgetTotal = 0.00;

Double comparisonTotal = 0.00;

for (Object key :map.keySet()){

data = new Vector();

int firmCode = Integer.parseInt(key.toString());

Double newRetail = newFinYrRetail.containsKey(firmCode) ? newFinYrRetail.get(firmCode) : 0.00;

Double newSbdy = newFinYrSbdy.containsKey(firmCode) ? newFinYrSbdy.get(firmCode) : 0.00;

Double oldRetail = lastFinYrRetail.containsKey(firmCode) ? lastFinYrRetail.get(firmCode) : 0.00;

Double oldSbdy = lastFinYrSbdy.containsKey(firmCode) ? lastFinYrSbdy.get(firmCode) : 0.00;

Double budgetValue = budgetData.containsKey(firmCode) ? budgetData.get(firmCode) : 0.00;

//System.out.println(firmCode +"--->"+budgetValue);

Double variation = (newRetail + newSbdy) - (oldRetail + oldSbdy);

Double comparison = budgetValue!=0 ? (newRetail + newSbdy)*100/budgetValue : 0.00;

//inserting all values to array

data.add(serialNo); //1

data.add(map.get(firmCode)); //2

data.add(Double.parseDouble(decimalFormat.format(oldRetail))); //3

data.add(Double.parseDouble(decimalFormat.format(oldSbdy))); //4

data.add(Double.parseDouble(decimalFormat.format(newRetail))); //5

data.add(Double.parseDouble(decimalFormat.format(newSbdy))); //6

data.add(Double.parseDouble(decimalFormat.format(variation))); //7

data.add(budgetValue); //8

data.add(decimalFormat.format(comparison)); //9

//Grand Total calculation

oldRetailTotal =  oldRetailTotal + Double.parseDouble(decimalFormat.format(oldRetail));

oldSbdyTotal =  oldSbdyTotal + Double.parseDouble(decimalFormat.format(oldSbdy));

newRetailTotal = newRetailTotal + Double.parseDouble(decimalFormat.format(newRetail));

newSbdyTotal =  newSbdyTotal + Double.parseDouble(decimalFormat.format(newSbdy));

variationTotal = variationTotal + Double.parseDouble(decimalFormat.format(variation));

budgetTotal = budgetTotal + budgetValue;

//System.out.println(" String : "+comparison);

comparisonTotal = comparisonTotal + Double.parseDouble(decimalFormat.format(comparison));

//System.out.println(map.get(key));

//System.out.println(" firmcode :"+ firmCode +" variation : "+Variation + "comparison : "+comparison);

serialNo = serialNo +1;

array.add(data);

}

Vector footer = new Vector();

footer.add(" ");

footer.add(" GRAND TOTAL ");

footer.add(oldRetailTotal);

footer.add(oldSbdyTotal);

footer.add(newRetailTotal);

footer.add(newSbdyTotal);

footer.add(variationTotal);

footer.add(budgetTotal);

footer.add(comparisonTotal);

array.add(footer);

return array;

}

}

dependency jar : jxl.jar

git clone : https://github.com/consumerfed/BudgetPreparation.git

Bloom filter

The concept of bloom filter

Find the odd one from a non empty integer array in java

Given a non-empty array of integers, every element appears twice except for one. Find that single one.

class Cfed{

public int singleNumber(int[] nums) {

int length = nums.length;

for (int i = 0; i < length - 1; i++) {

if (nums[i] > nums[i + 1]) {

int temp = nums[i];

nums[i] = nums[i + 1];

nums[i + 1] = temp;

i = -1;

}

}

int i = 0;

int ans = nums[length-1];

while (i+1 < length) {

if(nums[i]!=nums[i+1]) {

ans =  nums[i];

break;

}

i+=2;

}

return ans;

}

public static void main(String[] args) {

Cfed s = new Cfed();

int[] nums = { 4,1,2,1,2 }; 

System.out.println(s.singleNumber(nums));

}

}