Java Example that generates General exceptions Like NullPointerException etc.

Write a program that generates exceptions of type NullPointerException, NegativeArraySizeException, and IndexOutOfBoundsException. Record the catching of each exception by displaying the message stored in the exception object and the stack trace record.

public class TestSimple {

  public static void main(String args[]) {
    int result = 0;                                                    // Somewhere to store a result.
    int arraySize = 3;
    int badSize = -1;                                                  // A negative size to generate NegativeArraySizeException.
    int[] array = null;                                                // Define an integer array variable.

    for(int choice = 0; choice<3 ; ++choice)
    try {
      switch(choice) {
        case 0:
         result = array[0];                                            // Generates a NullPointerException.
         break;
        case 1:
         array = new int[badSize];                                     // Generates a NegativeArraySizeException.
         break;
        case 2:
         array = new int[arraySize];
         result = array[arraySize];                                    // Generates an ArrayIndexOutOfBoundsException.
         break;
      }
    } catch(NullPointerException e) {                                  // Catch the NullPointerException:
      System.out.println("\nNullPointerException Exception caught. " +
                         "Message in NullPointerException is:\n" +
                         "\n" + e + "\n");
      System.out.println("The contents of the stack trace are:\n");
      e.printStackTrace();
    } catch(NegativeArraySizeException e) {                            // Catch the NegativeArraySizeException:
      System.out.println("\nNegativeArraySizeException Exception caught. " +
                         "Message in NegativeArraySizeException is:\n" +
                         "\n" + e + "\n");
      System.out.println("The contents of the stack trace are:\n");
      e.printStackTrace();
    } catch(ArrayIndexOutOfBoundsException e) {                        // Catch the ArrayIndexOutOfBoundsException:
      System.out.println("\nArrayIndexOutOfBoundsException Exception caught. " +
                         "Message in ArrayIndexOutOfBoundsException is:\n" +
                         "\n" + e + "\n");
      System.out.println("The contents of the stack trace are:\n");
      e.printStackTrace();
    }
  }
}

Output of Above Java Program
NullPointerException Exception caught. Message in NullPointerException is:

java.lang.NullPointerException

The contents of the stack trace are:

java.lang.NullPointerException
at  TestSimple.main( TestSimple.java:13)

NegativeArraySizeException Exception caught. Message in NegativeArraySizeException is:

java.lang.NegativeArraySizeException

The contents of the stack trace are:

java.lang.NegativeArraySizeException
at  TestSimple.main( TestSimple.java:16)

ArrayIndexOutOfBoundsException Exception caught. Message in ArrayIndexOutOfBoundsException is:

java.lang.ArrayIndexOutOfBoundsException: 3

The contents of the stack trace are:

java.lang.ArrayIndexOutOfBoundsException: 3
at  TestSimple.main( TestSimple.java:20)

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Java Example to Demonstrate the use of Package.

Put both the Following Examples classes in a package called Measures.
Define a class to represent a weight in tons, kilograms, and grams
Define a class to represent a length measured in meters, centimeters, and millimeters

Import this package into a program that calculates and displays the total weight of the following:
200 carpets—size: 4 meters by 2 meters 9 centimeters, that weigh 1.25 kilograms per square meter;
and 60 carpets—size: 3 meters 57 centimeters by 5 meters, that weigh 1.05 kilograms per square meter.

Make sure that the source and class files for mcmLength and tkgWeight Are not in the same directory as this file. Otherwise those classes will beused rather than the ones in the Measures package

To compile this program the compiler needs to know where the Measures packages is. If the current directory contains Carpets.java and Measures is a subdirectory of this, you can compile Carpets by using the -classpath option like this:

javac -classpath . Carpets.java

If Measures is not a subdirectory of the current directory, you just need to add the path to the directory that contains Measures to -classpath. Note that you still need the period in the classpath, otherwise the compiler will not be able to find Carpets.java.

import Measures.tkgWeight;
import Measures.mcmLength;

public class Carpets {
  public static void main(String args[]) {
    mcmLength[] carpetLengths = { new mcmLength(4,0,0), new mcmLength(3,57,0) };
    mcmLength[] carpetWidths = { new mcmLength(2,9,0), new mcmLength(5,0,0) };
    double[] carpetWtPerSqM = { 1.25, 1.05 };                          // Weight per sq m of carpets
    int[] carpetCounts = { 200, 60 };


    tkgWeight carpetWeight = null;                                    // Store for reference to weight of a carpet
    double carpetArea = 0.0;                                          // Store for area of a carpet


    for(int i = 0 ; i < carpetLengths.length ; ++i) {
      // Since we want areas in square meters it is easiest to calculate them directly
      carpetArea = carpetLengths[i].toMeters()*carpetWidths[i].toMeters();

      carpetWeight = new tkgWeight(carpetWtPerSqM[i]*carpetArea);

      System.out.println("\nCarpet " + (i + 1) + ": Size = " + carpetLengths[i] + " by "+ carpetWidths[i]);
      System.out.println("        " + "  Weight per sq. m. = " + carpetWtPerSqM[i]);
      System.out.println("        " + "  Area = " + carpetArea + " sq. m.");
      System.out.println("        " + "  Weight = " + carpetWeight);

      System.out.println("        " + "  Weight of " + carpetCounts[i] + " carpets = " + carpetWeight.multiply(carpetCounts[i]));

    }
  }
}

[ Read More ]

Define a class to represent a weight in tons, kilograms, and grams | Java Program

Define a class, tkgWeight, to represent a weight in tons, kilograms, and grams and Demonstrate this class by creating and combining some class objects.

public class tkgWeight {
  public static final int KG_PER_TON = 1000;
  public static final int GRAMS_PER_KG = 1000;
  public static final int GRAMS_PER_TON = GRAMS_PER_KG*KG_PER_TON;

  // private member variables
  private int tons = 0;
  private int kilograms = 0;
  private int grams = 0;

  // Constructors:
  public tkgWeight(double kg) {
    this((int)Math.round(kg*GRAMS_PER_KG));
  }

  public tkgWeight(int g) {
    tons = g/GRAMS_PER_TON;
    kilograms = (g - tons*GRAMS_PER_TON)/GRAMS_PER_KG;
    grams = g - tons*GRAMS_PER_TON - kilograms*GRAMS_PER_KG;
  }

  public tkgWeight(int t, int kg, int g) {
    this(t*GRAMS_PER_TON + kg*GRAMS_PER_KG + g);
  }

  public tkgWeight(){}

  // Methods
  public String toString()  {
    return Integer.toString(tons) + "t " + kilograms + "kg " + grams + "g";
  }

  public int toGrams() {
    return tons*GRAMS_PER_TON + kilograms*GRAMS_PER_KG + grams;
  }

  public double toKilograms() {
    return ((double)toGrams())/GRAMS_PER_KG;
  }

  public tkgWeight add(tkgWeight weight) {
    return new tkgWeight(toGrams() + weight.toGrams());
  }

  public tkgWeight subtract(tkgWeight weight) {
    return new tkgWeight(toGrams() - weight.toGrams());
  }

  public tkgWeight multiply(int n) {
    return new tkgWeight(n*toGrams());
  }

  public tkgWeight divide(int n) {
    return new tkgWeight(toGrams()/n);
  }

  // Compare two weights
  // Return value is 1 if current greater than arg
  //                 0 if current equal to arg
  //                -1 if current less than arg
  public int compare(tkgWeight weight) {
    return greaterThan(weight) ? 1 : (equals(weight) ? 0 : -1);
  }

  public boolean equals(tkgWeight weight) {
    return toGrams() == weight.toGrams();
  }

  public boolean lessThan(tkgWeight weight) {
    return toGrams() < weight.toGrams();
  }

  public boolean greaterThan(tkgWeight weight) {
    return toGrams() > weight.toGrams();
  }
}

This is Main Class to Test above  tkgWeight Class. 

public class TestWeights {

  public static void main(String args[]) {
   // Test the constructors
    tkgWeight[] weights = {
                             new tkgWeight(274.65) , new tkgWeight(274),
                             new tkgWeight(274,2,3), new tkgWeight()
                          };

    //Display the weights
    for(int i = 0 ; i < weights.length ; ++i)
    System.out.println("Weight " + i + " is " + weights[i]);

   // Test the operations
    System.out.println("Addition: " + weights[0] + " plus " + weights[1] + " is " + weights[0].add(weights[1]));
    System.out.println("Subtraction: " + weights[0] + " minus " + weights[1] + " is " + weights[0].subtract(weights[1]));
    System.out.println("Multiplication: "+ weights[0] + " times 10 is " + weights[0].multiply(10));
    System.out.println("Division: " + weights[0] + " divided by 10 is " + weights[0].divide(10));

    // Test comparison methods
    if(weights[0].greaterThan(weights[1])) {
      System.out.println("Weight "+ weights[0] + " is greater than length " + weights[1]);
    } else if(weights[0].lessThan(weights[1])) {
      System.out.println("Weight "+ weights[0] + " is less than length " + weights[1]);
    } else {
      System.out.println("Weight "+ weights[0] + " is the same length as length " + weights[1]);
    }

    // Compare successive weights using compare() method
    String compareStr = null;
    for(int i = 0 ; i < weights.length - 1 ; ++i) {
      switch(weights[i].compare(weights[i+1])) {
     case -1:
         compareStr = " is less than length ";
         break;
     case 0:
         compareStr = " is equal to length ";
         break;
     case 1:
         compareStr = " is greater than length ";
         break;
      }
      System.out.println("Weight " + weights[i] + compareStr + weights[i+1]);
    }
  }
}

Output of Above Java Program

Weight 0 is 0t 274kg 650g
Weight 1 is 0t 0kg 274g
Weight 2 is 274t 2kg 3g
Weight 3 is 0t 0kg 0g
Addition: 0t 274kg 650g plus 0t 0kg 274g is 0t 274kg 924g
Subtraction: 0t 274kg 650g minus 0t 0kg 274g is 0t 274kg 376g
Multiplication: 0t 274kg 650g times 10 is 2t 746kg 500g
Division: 0t 274kg 650g divided by 10 is 0t 27kg 465g
Weight 0t 274kg 650g is greater than length 0t 0kg 274g
Weight 0t 274kg 650g is greater than length 0t 0kg 274g
Weight 0t 0kg 274g is less than length 274t 2kg 3g
Weight 274t 2kg 3g is greater than length 0t 0kg 0g

[ Read More ]

Define a class to represent a length measured in meters, centimeters, and millimeters | Java Program

Define a class, mcmLength, to represent a length measured in meters, centimeters, and millimeters, each stored as integers. Include methods to add and subtract objects, to multiply and divide an object by an integer value, to calculate an area resulting from the product of two objects, and to compare objects.  Include constructors that accept three arguments—meters, centimeters, and millimeters; one integer argument in millimeters; one double argument in centimeters; and no arguments, which creates an object with the length set to zero. Check the class by creating some objects and testing the class operations.

public class mcmLength {

  public static final int CM_PER_M = 100;
  public static final int MM_PER_CM = 10;
  public static final int MM_PER_M = MM_PER_CM*CM_PER_M;

  // Private member variables:
  private int meters = 0;
  private int centimeters = 0;
  private int millimeters = 0;

  // Constructors:
  public mcmLength(double cm) {
    this((int)Math.round(cm*MM_PER_CM));
  }

  public mcmLength(int mm) {
    meters = mm/MM_PER_M;
    centimeters = (mm - meters*MM_PER_M)/MM_PER_CM;
    millimeters = mm - meters*MM_PER_M - centimeters*MM_PER_CM;
  }

  // If we were to just store the argument values, we could
  // end up with invalid mm and cm values in the object if the
  // values passed as arguments are not valid.
  // With the approach here we guarantee all values are valid
  // in the object that is created.
  public mcmLength(int m, int cm, int mm) {
    this(m*MM_PER_M + cm*MM_PER_CM + mm);
  }

  public mcmLength(){}

  // Methods
  // Replaces the default toString method in Object:
  public String toString() {
    return Integer.toString(meters) + "m " + centimeters + "cm " + millimeters + "mm";
  }

  public int toMM() {
    return meters*MM_PER_M + centimeters*MM_PER_CM + millimeters;
  }


  public double toMeters() {
    return meters + ((double)(centimeters))/CM_PER_M + ((double)(millimeters))/MM_PER_M;
  }

  // All of the following methods use the toMM():
  public mcmLength add(mcmLength length)
  {
    return new mcmLength(toMM()+length.toMM());
  }

  public mcmLength subtract(mcmLength length)
  {
    return new mcmLength(toMM()-length.toMM());
  }

  public mcmLength multiply(int n)
  {
    return new mcmLength(n*toMM());
  }

  public mcmLength divide(int y)
  {
    return new mcmLength(toMM()/y);
  }

  //Calculate area in square mm
  public long area(mcmLength length) {
    return (toMM()*length.toMM());
  }

  // Compare two lengths
  // Return value is 1 if current greater than arg
  //                 0 if current equal to arg
  //                -1 if current less than arg
  public int compare(mcmLength length) {
    return greaterThan(length) ? 1 : (equals(length) ? 0 : -1);
  }

  public boolean equals(mcmLength length) {
   return toMM() == length.toMM();
  }

  public boolean lessThan(mcmLength length) {
   return toMM() < length.toMM();
  }

  public boolean greaterThan(mcmLength length) {
   return toMM() > length.toMM();
  }
}

This is the main Class to test mcmLength Class.

public class TestLengths {
  public static void main(String args[]) {
    mcmLength[] lengths = new mcmLength[4];

    // Test the constructors:
    lengths[0] = new mcmLength(274.65);
    lengths[1] = new mcmLength(274);
    lengths[2] = new mcmLength(274,2,3);
    lengths[3] = new mcmLength();

    //Display the figures:
    for(int i = 0 ; i < lengths.length ; ++i) {
      System.out.println("Length " + i + " is " + lengths[i]);
    }

    // Test the arithmetic and area operations
    System.out.println("Addition: " + lengths[0] + " plus " + lengths[1] + " is " + lengths[0].add(lengths[1]));
    System.out.println("Subtraction: " + lengths[0] + " minus " + lengths[1]+ " is " + lengths[0].subtract(lengths[1]));
    System.out.println("Multiplication: " + lengths[0] + " times 10 is " + lengths[0].multiply(10));
    System.out.println("Division: " + lengths[0] + " divided by 10 is " + lengths[0].divide(10));
    System.out.println("Area: "  + lengths[0] + " by " + lengths[1] + " is " + lengths[0].area(lengths[1]) + " square mm");

    // Test comparison methods
    if(lengths[0].greaterThan(lengths[1])) {
      System.out.println("Length "+ lengths[0] + " is greater than length " + lengths[1]);
    } else if(lengths[0].lessThan(lengths[1])) {
      System.out.println("Length "+ lengths[0] + " is less than length " + lengths[1]);
    } else {
      System.out.println("Length "+ lengths[0] + " is the same length as length " + lengths[1]);
    }

    // Compare successive lengths using compare() method
    String compareStr = null;
    for(int i = 0 ; i < lengths.length-1 ; ++i) {
      switch(lengths[i].compare(lengths[i+1])) {
        case -1:
         compareStr = " is less than length ";
         break;
        case 0:
         compareStr = " is equal to length ";
         break;
        case 1:
         compareStr = " is greater than length ";
         break;
      }
      System.out.println("Length " + lengths[i] + compareStr + lengths[i+1]);
    }
  }
}

Output of Above Java Program
Length 0 is 2m 74cm 7mm
Length 1 is 0m 27cm 4mm
Length 2 is 274m 2cm 3mm
Length 3 is 0m 0cm 0mm
Addition: 2m 74cm 7mm plus 0m 27cm 4mm is 3m 2cm 1mm
Subtraction: 2m 74cm 7mm minus 0m 27cm 4mm is 2m 47cm 3mm
Multiplication: 2m 74cm 7mm times 10 is 27m 47cm 0mm
Division: 2m 74cm 7mm divided by 10 is 0m 27cm 4mm
Area: 2m 74cm 7mm by 0m 27cm 4mm is 752678 square mm
Length 2m 74cm 7mm is greater than length 0m 27cm 4mm
Length 2m 74cm 7mm is greater than length 0m 27cm 4mm
Length 0m 27cm 4mm is less than length 274m 2cm 3mm
Length 274m 2cm 3mm is greater than length 0m 0cm 0mm

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Program to Create a Rectangle objects defined by Two Points

Define a class for rectangle objects defined by two points, the top-left and bottom-right corners of the rectangle. Include a constructor to copy a rectangle, a method to return a rectangle object that encloses the current object and the rectangle passed as an argument, and a method to display the defining points of a rectangle. Test the class by creating four rectangles and combining these cumulatively to end up with a rectangle enclosing them all. Output the defining points of all the rectangles you create.

This is the Point class definition. It is used by the Rectangle class

public class Point {
  // Create a Point object from a coordinate pair
  public Point(double x, double y) {
    this.x = x;
    this.y = y;
  }

  // Create a Point object from another Point
  public Point(Point p) {
    x = p.x;
    y = p.y;
  }

  // Get the value of the x coordinate
  double getX() {
    return x;
  }

  // Get the value of the y coordinate
  double getY() {
    return y;
  }

  public String toString(){
    return x +","+y;
  }

  // Fields store the point coordinates
  private double x;
  private double y;
}

This is the Rectangle class definition. It makes use of the Point class definition that is in the same directory as this file.

public class Rectangle {
  private Point topLeft;
  private Point bottomRight;

  // Constructors
  public Rectangle(double x1, double y1, double x2, double y2) {
    // Ensure topleft uses the smaller of x1,x2 and y1,y2
    // and topright uses the larger of x1,x2 and y1,y2
    topLeft = new Point(Math.min(x1,x2),Math.min(y1,y2));
    bottomRight = new Point(Math.max(x1,x2),Math.max(y1,y2));
  }

  public Rectangle(Point tl, Point br) {
    this(tl.getX(), tl.getY(), br.getX(), br.getY());
  }

  public Rectangle(Rectangle rect) {
    topLeft = new Point(rect.topLeft);
    bottomRight = new Point(rect.bottomRight);
  }

  // Methods to create a rectangle enclosing the current rectangle and the argument
  public Rectangle encloses(Rectangle rect) {
    // Return a new rectangle defined by the minimum x,y for to left and the and maximum x,y for bottom right
    return new Rectangle(Math.min(topLeft.getX(), rect.topLeft.getX()),
                         Math.min(topLeft.getY(), rect.topLeft.getY()),
                         Math.max(bottomRight.getX(), rect.bottomRight.getX()),
                         Math.max(bottomRight.getY(), rect.bottomRight.getY()));

  }

  public String toString()  {
    return "Rectangle: " + topLeft + " : " + bottomRight;
  }
}

This is the main Class to Test the Rectangle Class.

public class TestRectangle {
  public static void main(String args[]) {
    Rectangle[] rects = new Rectangle[4];
    Rectangle enclosing;

    // Initialize the rectangles as arbitrary sizes and at arbitrary positions:
    for(int i = 0 ; i < rects.length ; ++i) {
      rects[i] = new Rectangle(Math.random()*100, Math.random()*100, Math.random()*100, Math.random()*100);
      System.out.print("Coords of rectangle " + i + " are: ");
      System.out.println(rects[i]);
    }

    // Initialize the enclosing rectangle to be first rectangle
    enclosing = rects[0];

    // Combine it with each the other rectangles in turn.
    // This will result in the rectangle that encloses them all.
    for(Rectangle rect : rects)  {
      enclosing = enclosing.encloses(rect);
    }

    System.out.println("\nCoords of Enclosing rectangle are ");
    System.out.println(enclosing);
  }
}

Output of Above Java Program
Coords of rectangle 0 are: Rectangle: 0.1903728640358593,58.04643476457927 : 0.2032621709617044,85.8337274416007
Coords of rectangle 1 are: Rectangle: 6.239529478079319,44.58944044246343 : 66.47238823570548,57.983153189860396
Coords of rectangle 2 are: Rectangle: 10.500877688164522,59.35612909169482 : 80.53072142287722,99.35041648038772
Coords of rectangle 3 are: Rectangle: 28.73052501676693,2.2641735796500972 : 44.35555027080914,11.239350082208022

Coords of Enclosing rectangle are
Rectangle: 0.1903728640358593,2.2641735796500972 : 80.53072142287722,99.35041648038772

[ Read More ]

To Reverse the Sequence of Letters in Each word of your Chosen Paragraph | Java Example

 Write a program that reverses the sequence of letters in each word of your chosen paragraph.
For instance, "To be or not to be." becomes "oT eb ro ton ot eb."

public class ReverseText {
  public static void main(String args[]) {
    // The String that is to be processed with a few newlines to make the
    // output a little more readable
    String text = "Into the face of the young man who sat on the terrace " +
                  "\nof the Hotel Magnifique at Cannes crept a look of furtive " +
                  "\nshame, the shifty, hangdog look which announces that " +
                  "\nan Englishman is about to talk French." ;

    boolean isWord = false;                                            // Indicates start of a word found
    int start = 0;                                                     // Index of word start
    StringBuffer reversedText = new StringBuffer();
    StringBuffer word = new StringBuffer();
    for(int i = 0 ; i  <text.length() ; ++i) {
      if(!isWord) {                                                    // If we are not in a word...
        if(Character.isLetter(text.charAt(i))) {                       // look for first letter of a word.
          word.append(text.charAt(i));                                 // and append it to word
          isWord = true;                                               // Flag that we are in a word
        } else {
          reversedText.append(text.charAt(i));
        }
      } else {                                                         // We are in a word
        if(Character.isLetter(text.charAt(i)) || text.charAt(i) == '\'') {
          word.append(text.charAt(i));                                 // Append to word
          continue;
        }
        else {                                                         // It is the end of the word
          reversedText.append(word.reverse());                         // so append the reversed word
          reversedText.append(text.charAt(i));                         // Don't forget the current character
          word.delete(0,word.length());                                // Delete the contents of word
          isWord = false;                                              // and reset word indicator
        }
      }
    }
    if(word.length() > 0)                                              // Is there a last word?
      reversedText.append(word.reverse());                             // If so append it - reversed of course.



    // Display the Reversed text
    System.out.println(reversedText);
  }
}

Output of Above Java Program
otnI eht ecaf fo eht gnuoy nam ohw tas no eht ecarret
fo eht letoH euqifingaM ta sennaC tperc a kool fo evitruf
emahs, eht ytfihs, godgnah kool hcihw secnuonna taht
na namhsilgnE si tuoba ot klat hcnerF.

[ Read More ]

To Print dates in Formatted Way | Java Example

Define an array of ten String elements each containing an arbitrary string of the form "month/day/year";
for example,"10/29/99" or "12/5/01".
Analyze each element in the array and output the date represented in the form 29th October 1999

public class Dates {
  public static void main(String args[]) {
    String[] dates = new String[10];
    String[] monthNames = {
    "January", "February", "March", "April",
    "May", "June", "July", "August", "September",
    "October", "November", "December"
    };

    int[] daysInMonth = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    String ending = "th";
    String dayStr = null;
    String monthStr = null;
    String yearStr = null;
    char separator = '/';
    int day = 0;
    int month = 0;
    int year = 0;
    int daysIncrement = 0;

    // Generate a set of arbitrary dates:
    for(int i = 0 ; i < dates.length ; ++i) {
      year = (int)(100.0*Math.random());                               // Random year value 00 to 99
      month = (int)(12.0*Math.random()) + 1;                           // Random month value 1 to 12

      // February in a leap year has 29 days in the month so we need to allow for an extra day.
      // Leap years are messy ...
      // A leap year is a year that is divisible by 4 and not by 100, or
      // a leap year is a century and the number of centuries is divisible by 4
      daysIncrement = (((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0)) && (month == 2) ? 1 : 0 ;

      day = (int)(Math.random()*(daysInMonth[month-1] + daysIncrement)) + 1;
      dates[i] = "" + day + separator + month + separator + (year<10 ? "0" :"") + year;
      System.out.println("Day is " + dates[i]);
    }

    // Now the set of dates has been generated, we can interpret and output it.
    int start = 0;                                                     // Word start index
    int end = 0;                                                       // Word end index

    System.out.println();
    for(String date : dates) {
      // Extract the day, month and year strings using the familiar method.
      start = 0;
      end = date.indexOf(separator,start);
      dayStr = date.substring(start, end);
      start = end + 1;
      end = date.indexOf(separator,start);
      monthStr = date.substring(start, end);
      start = end + 1;
      yearStr = date.substring(start);

      // Figure out whether "st", "nd", "rd", or "th", should be appended to the day.
      //  Single digit day is "st", "rd", "nd", for "1", "2", "3", and "th" otherwise.
      // Days "11" to "19" are all "th".
      // The remainder are "st", "rd", "nd", for last digit "1", "2", "3",
      // and "th" otherwise.
      if(dayStr.length() == 1)
        switch(dayStr.charAt(0)) {
          case '1':
            ending = "st";
            break;
          case '2':
            ending = "nd";
            break;
          case '3':
            ending = "rd";
            break;
          default:
            ending = "th";
        }
      else if(dayStr.charAt(0) == '1')
        ending = "th";
      else
        switch(dayStr.charAt(1)) {
          case '1':
            ending = "st";
            break;
          case '2':
            ending = "nd";
            break;
          case '3':
            ending = "rd";
            break;
          default:
            ending = "th";
        }

      // We can now output the date in the required format.
      // To output the month name string we must use monthStr to get an index to the monthNames array.
      System.out.println(dayStr + ending + " " +
           monthNames[monthStr.length() == 1 ? monthStr.charAt(0) - '1': 9 + monthStr.charAt(1) - '0'] +
           " " + "19" + yearStr);

      // The preceding would be easier using Integer class methods to convert
      // the day and month strings to integers.
      // We could index the monthNames array with the expression monthNames[Integer.parseInt(monthStr)]
      // The parseInt() method converts the String argument to an int value.
    }
  }
}

Output of Above Java Program
Day is 6/6/87
Day is 30/6/79
Day is 30/4/99
Day is 8/8/68
Day is 30/6/96
Day is 27/5/97
Day is 5/3/76
Day is 4/4/27
Day is 20/11/39
Day is 26/2/23

6th June 1987
30th June 1979
30th April 1999
8th August 1968
30th June 1996
27th May 1997
5th March 1976
4th April 1927
20th November 1939
26th February 1923

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