Javascript

    /*Exercise 9 - 1: Average*/
    public static void main(String[] args) {
        int[] anArray = {13, 20, 7, 25, 2, 14, 9, 100};
        double average, sum = 0;

        for(int i = 0; i < anArray.length; i++)
        {
            sum += anArray[i];
        }
        average = sum/anArray.length;

        System.out.println("Average value of the array elements is: " + average);
    }


/*-------------------------------------------------------------------------------------------------------------------------*/
 /*Exercise 9 - 2: Odd number*/
    public static void main(String[] args) {
        int[] anArray = {184, 117, 81, 157, 209, 40, 58};
        double average, sum = 0;

        for(int i = 0; i < anArray.length; i++)
        {
            if(anArray[i] % 2 != 0)
            {
                System.out.println("odd number = " + anArray[i]);
            }
        }
    }


/*-------------------------------------------------------------------------------------------------------------------------*/
    /*Exercise 9 - 3: Triangle*/
    public static void main(String[] args) {
        int length;
        Scanner sc = new Scanner(System.in);

        System.out.print("Please input the length of the triangle: ");
        length = sc.nextInt();

        int[][] triangle = new int[length][length];
        for(int height = 0; height <= triangle.length; height++)
        {
            for(int width = 0; width < height; width++)
            {
                System.out.print("*");
        System.out.print(width + ",");
            }
            System.out.println("");
        }
    }


/*-------------------------------------------------------------------------------------------------------------------------*/
 /*Exercise 11 - 3: Generate random string*/
    public static void GenerateRandomString(int stringLength, String aString)
    {
        Random generate = new Random();
        StringBuilder rb = new StringBuilder();
        char c;

        for(int i = 0; i < stringLength; i++)
        {
            if(aString.length() < stringLength)
            {
                c = aString.charAt(generate.nextInt(aString.length()));
            }
            else
            {
                c = aString.charAt(generate.nextInt(stringLength));
            }
            rb.append(c);
        }
        System.out.println("Your string is: " + rb);
    }

    public static void main(String[] args) {
        int length;
        String randomString;
        Scanner sc = new Scanner(System.in);

        System.out.print("Input your string length: ");
        length = sc.nextInt();

        System.out.print("Chars to use for random string generation: ");
        randomString = sc.next();

        GenerateRandomString(length, randomString);
    }


/*-------------------------------------------------------------------------------------------------------------------------*/
 /*Exercise 11 - 3: Generate random string*/
    public static void GenerateRandomString(int stringLength, String aString)
    {
        Random generate = new Random();
        StringBuilder rb = new StringBuilder();
        char c;

        for(int i = 0; i < stringLength; i++)
        {
            if(aString.length() < stringLength)
            {
                c = aString.charAt(generate.nextInt(aString.length()));
            }
            else
            {
                c = aString.charAt(generate.nextInt(stringLength));
            }
            rb.append(c);
        }
        System.out.println("Your string is: " + rb);
    }

    public static void main(String[] args) {
        int length;
        String randomString;
        Scanner sc = new Scanner(System.in);
        //Scanner sc1 = new Scanner(System.in);

        System.out.print("Input your string length: ");
        length = sc.nextInt();
        sc.nextLine();
        System.out.print("Chars to use for random string generation: ");
        randomString = sc.nextLine();

        if(randomString.isEmpty())
        {
            System.out.println("User default charSet a-z,A-z,0-9 to random String");
            randomString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        }
        GenerateRandomString(length, randomString);
    }



/*-------------------------------------------------------------------------------------------------------------------------*/
 /*Exercise 11 - 4: Generate random string 2*/
    public static void GenerateRandomString(int stringLength, String aString)
    {
        Random generate = new Random();
        StringBuilder rb = new StringBuilder();
        char c;

        for(int i = 0; i < stringLength; i++)
        {
            if(aString.length() < stringLength)
            {
                c = aString.charAt(generate.nextInt(aString.length()));
            }
            else
            {
                c = aString.charAt(generate.nextInt(stringLength));
            }
            rb.append(c);
        }
        System.out.println("Your string is: " + rb);
    }

    public static void main(String[] args) {
        int length;
        String randomString;
        Scanner sc = new Scanner(System.in);
        //Scanner sc1 = new Scanner(System.in);

        System.out.print("Input your string length: ");
        length = sc.nextInt();
        sc.nextLine();
        System.out.print("Chars to use for random string generation: ");
        randomString = sc.nextLine();

        if(randomString.isEmpty())
        {
            System.out.println("User default charSet a-z,A-z,0-9 to random String");
            randomString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        }
        GenerateRandomString(length, randomString);
    }


/*-------------------------------------------------------------------------------------------------------------------------*/
   /*Exercise 11 - 5: Choose random*/
    public static String chooseRandom(String[] stringArray)
    {
        Random r = new Random();
        int i = r.nextInt(stringArray.length);

        return stringArray[i];
    }

    public static void main(String[] args) {
        String[] aStringArray = {"Red", "Blue", "Orange", "Purple", "White", "Pink", "Yellow", "Colour"};

        System.out.println("Your item is: " + chooseRandom(aStringArray));
    }



/*-------------------------------------------------------------------------------------------------------------------------*/
   /*Exercise 13 - 1: Verify username*/
    public static void CreateFile(String[] stringArray) throws IOException
    {
        String dir = System.getProperty("user.dir");

        File f = new File(dir + File.separator + "user.txt");

        f.createNewFile();

        FileWriter writer = new FileWriter(f);
        BufferedWriter buffer = new BufferedWriter(writer);
        PrintWriter printWriter = new PrintWriter(buffer);

        for(String s : stringArray) {
            printWriter.println(s);
        }

        printWriter.close();
        writer.close();
        buffer.close();
    }

    public static boolean CheckUsername(String aDir, String aName) throws IOException
    {
        FileReader fr = new FileReader(aDir);
        BufferedReader br = new BufferedReader(fr);
        String s;

        System.out.println("Checking if username exists...");
        while ((s = br.readLine()) != null) {
            if (s.equals(aName)) {
                return true;
            }
        }
        return false;
    }


    public static void main(String[] args) throws IOException {
        //Create a user text file
        String[] username = {"Ronda",
                "Stephan",
                "Illa",
                "Isabelle",
                "Nelson",
                "Juana",
                "Earlie",
                "Velda",
                "Linnie",
                "Mana",
                "Rosario",
                "Jolyn",
                "Merry",
                "Anika",
                "Carlotta",
                "Breann",
                "Jennine",
                "Larue",
                "Enola",
                "Pauline"};

        CreateFile(username);

        /*Exercise 13 - 1*/
        Scanner sc = new Scanner(System.in);
        String inputName;

        System.out.print("Enter your username: ");
        inputName = sc.next();

        String dir = System.getProperty("user.dir") + File.separator + "user.txt";
        if (CheckUsername(dir, inputName))
        {
            System.out.println("Username exists! Please try again.");
        }
        else
        {
            System.out.println("Username is accepted.");
        }
    }
}



/*-------------------------------------------------------------------------------------------------------------------------*/
  /*Exercise 13 - 2: Compare 2 files*/
    public static void main(String[] args) throws IOException {
        //Reader for compare1
        String dir1 = System.getProperty("user.dir") + File.separator + "compare1.txt";
        FileReader fr1 = new FileReader(dir1);
        BufferedReader br1 = new BufferedReader(fr1);
        String s1;

        //Reader for compare2
        String dir2 = System.getProperty("user.dir") + File.separator + "compare2.txt";
        FileReader fr2 = new FileReader(dir2);
        BufferedReader br2 = new BufferedReader(fr2);
        String s2;

        //Writer for compare
        File f = new File(System.getProperty("user.dir") + File.separator + "compare.txt");
        f.createNewFile();
        FileWriter writer = new FileWriter(f);
        BufferedWriter buffer = new BufferedWriter(writer);
        PrintWriter printWriter = new PrintWriter(buffer);

        //Loop through compare1 and compare2
        while ((s1 = br1.readLine()) != null)
        {
            while ((s2 = br2.readLine()) != null) {
                if(s1.equals(s2))
                {
                    printWriter.println(s1);
                }
            }
            //Refresh buffer to the top of the file
            fr2 = new FileReader(dir2);
            br2 = new BufferedReader(fr2);
        }
        printWriter.close();
        buffer.close();
        writer.close();
        br1.close();
        br2.close();
        fr1.close();
        fr2.close();
    }


/*-------------------------------------------------------------------------------------------------------------------------*/
  /*Exercise 13 - 3: Count number of lines in file*/
    public static void CreateFile(String[] stringArray) throws IOException
    {
        String dir = System.getProperty("user.dir");

        File f = new File(dir + File.separator + "text.txt");

        f.createNewFile();


        FileWriter writer = new FileWriter(f);
        BufferedWriter buffer = new BufferedWriter(writer);
        PrintWriter printWriter = new PrintWriter(buffer);

        for(String s : stringArray) {
            printWriter.println(s);
        }

        printWriter.close();
        writer.close();
        buffer.close();
    }

    public static void main(String[] args) throws IOException {
        //Create a text file
        String[] textFile = {"Ronda",
                "Stephan",
                "",
                "Illa",
                "Isabelle",
                "",
                "Nelson",
                "Juana",
                "Earlie",
                "Velda",
                "",
                "Linnie",
                "Mana",
                "Rosario",
                "Jolyn",
                "Merry",
                "",
                "Anika",
                "Carlotta",
                "Breann",
                "Jennine",
                "Larue",
                "",
                "Enola",
                "Pauline"};

        CreateFile(textFile);

        /*Exercise 13 - 3*/
        String dir = System.getProperty("user.dir") + File.separator + "text.txt";
        FileReader fr = new FileReader(dir);
        BufferedReader br = new BufferedReader(fr);
        String s;
        int numOfLine = 0;

        while ((s = br.readLine()) != null) {
            if(!s.equals(""))
            {
                numOfLine++;
            }
        }

        System.out.println("Number of lines is: " + numOfLine);
    }



/*-------------------------------------------------------------------------------------------------------------------------*/
    /*Exercise 13 - 4: Remove all blank line in file*/
    public static void CreateFile(String[] stringArray) throws IOException
    {
        String dir = System.getProperty("user.dir");

        File f = new File(dir + File.separator + "text.txt");

        f.createNewFile();


        FileWriter writer = new FileWriter(f);
        BufferedWriter buffer = new BufferedWriter(writer);
        PrintWriter printWriter = new PrintWriter(buffer);

        for(String s : stringArray) {
            printWriter.println(s);
        }

        printWriter.close();
        writer.close();
        buffer.close();
    }

    public static void CreateFile(String aString) throws IOException
    {
        String dir = System.getProperty("user.dir");

        File f = new File(dir + File.separator + "text.txt");

        f.createNewFile();


        FileWriter writer = new FileWriter(f);
        BufferedWriter buffer = new BufferedWriter(writer);
        PrintWriter printWriter = new PrintWriter(buffer);

        printWriter.print(aString);

        printWriter.close();
        writer.close();
        buffer.close();
    }

    public static void main(String[] args) throws IOException {
        //Create a text file with blanks
        String[] textFile = {"Ronda",
                "Stephan",
                "",
                "Illa",
                "Isabelle",
                "",
                "Nelson",
                "Juana",
                "Earlie",
                "Velda",
                "",
                "Linnie",
                "Mana",
                "Rosario",
                "Jolyn",
                "Merry",
                "",
                "Anika",
                "Carlotta",
                "Breann",
                "Jennine",
                "Larue",
                "",
                "Enola",
                "Pauline"};

        CreateFile(textFile);

        /*Exercise 13 - 4*/
        String dir = System.getProperty("user.dir") + File.separator + "text.txt";
        FileReader fr = new FileReader(dir);
        BufferedReader br = new BufferedReader(fr);
        String s, separator = System.getProperty("line.separator");
        int numOfLine = 0;

        StringBuilder sb = new StringBuilder();


        while ((s = br.readLine()) != null) {
            if(!s.equals(""))
            {
                //This creates a line break at the end of string
                sb.append(s + separator);
            }
            else
            {
                numOfLine++;
            }
        }

        System.out.println("Number of blank lines is: " + numOfLine);
        String newString = sb.toString();
        //remove the line break at the end of string
        CreateFile(newString.substring(0, newString.length() - separator.length()));
        br.close();
        fr.close();
    }