Question

JAVA PROG HW

Problem 1

1. In the src −→ edu.neiu.p2 directory, create a package named problem1. 2. Create a Java class named StringParser with the following:

• ApublicstaticmethodnamedfindIntegerthattakesaStringandtwocharvariables as parameters (in that order) and does not return anything.

• The method should find and print the integer value that is located in between the two characters. You can assume that the second char parameter will always follow the firstchar parameter. However, you cannot assume that the parameters will be different from each other. Print out the result in this format (where XX represents the integer value): Integer: XX

• You may not use any loops, conditional statements, or regex (including switch state- ments and the tertiary operator).

1

• You cannot assume that only valid integers or nothing will appear in between the specified characters. If the value is not valid or there is nothing in between the specified characters,printout"Invalid characters"followedbyprintingouttheresultofcalling the toString method on the exception object.

• Hint: Think about the methods that you can use to convert Strings to integers and whether they throw exceptions! Make sure to handle the most specific exception class (i.e. do NOT use the superclass Exception to catch the exception object).

3. Once you’ve created the method, run the StringParserTest class in the tests package to see if you’ve created the code correctly.

4. Tohelpyourselfdebugandtestyourcode,createaJavaclassnamedStringParserDemothat has the main method. In the main method include at least three examples. Note that for the examples below, the method call is provided, followed by the expected output.

StringParser.findInteger("rugtsbckgus!32*", '!', '*'); Expected Output:
Integer: 32

StringParser.findInteger("rujfbgl&%fkslga", '&', '%'); Invalid integer
java.lang.NumberFormatException: For input string: ""

StringParser.findInteger("rusbdi#1038#jjdksu", '#', '#'); Integer: 1038

Problem 2

1. In the src −→ edu.neiu.p2 directory, create a package named problem1.

2. Create a Java class named Complement with the following:

   • A public static method named onesComplement that takes a String as a parameter and returns a String that is the 1’s complement of the parameter.

   • If the String is not a valid binary number (i.e. only has 0s and 1s), you should throw an IllegalArgumentException with the message "Not a valid binary number".

   • You may not use any loops.

   • You may use one conditional statement, but it cannot include any else if or else blocks.

3. Once you’ve created the method, run the ComplementTest class in the tests package to see if you’ve created the code correctly.

4. To help yourself debug and test your code, create a Java class named ComplementDemo that has the main method. In the main method include at least three examples.

Problem 3

Now let’s put everything together in an object-oriented manner! 2

1. In the problem3 package, create a class named PositiveNumberStatistics that has the following:

   • A private double 1D array instance variable named numbers.

   • A constructor that takes one parameter, a 1D double array. The constructor should throw an IllegalArgumentException with the message "Array length of zero" if the parameter has a length of 0. If the exception is not thrown, the constructor should create the numbers array and copy every element from the parameter into the numbersinstance variable. However, if any of the elements are less than or equal to zero, the constructor should throw a NumberFormatException with the message "Non-positive value at index X" where X is the first index at which a non-positive value occurs.

   • A method named average that does not take any parameters and returns a double. The method should return the average of the numbers in the instance variable numbers. Note that you do not need to worry about whether the numbers instance variable has been created in this method because this method will only be usable if the constructor does not throw an exception.

2. Onceyou’vecreatedthemethod,runthePositiveNumberStatisticsTestclassinthetestspackage to see if you’ve created the code correctly.

3. Then, in the StatsDemo class in the problem3 folder, write the code to handle creating an object for each of the provided arrays in the main method and call the average method. You should handle any exceptions by printing out the result of calling the toString method on the exception object.

Answer 1

Solution 1

in this we cannot use any loops or conditional statement but waht we can use is indexOf() adn substring() methods of Java String class.
indexOf(char) -> returns first index of character in the string
indexof(char,int) -> return index of char in strign from index provided as second parameter
After we have the index of both the parameters we can use the Integer.parseInt() method on substring() from index1 to inde2 to get teh deisred output.
Code

public class StringParser{

    public static void findInteger(String str,char a,char b){

            //first index of characetr a

            int pos1=str.indexOf(a);

            //index of character b after postion of character a

            int pos2=str.indexOf(b,pos1+1);

            //now we apply parse method on teh substrign got

            //as per the above two indexes

            int num=Integer.parseInt(str.substring(pos1+1,pos2));

            System.out.println("Integer : "+num);

    }

  

    public static void main(String args[])

    {

        //uncomment to see output for others

        StringParser.findInteger("rugtsbckgus!32*", '!', '*');

        // StringParser.findInteger("rujfbgl&%fkslga", '&', '%');

        // StringParser.findInteger("rusbdi#1038#jjdksu", '#', '#');

      

    }

    

}

Output
StringParser.findInteger("rugtsbckgus!32*", '!', '*');

Solution 2

To solve this we can use the BigInteger class of Java which is in the java.math library
In order to check if the string has only 0 and 1 we can uses regex adn match method of java strign class as we can use one if sattement.

Code

import java.math.*;

public class Complement{

    

    public static String onesComplement(String a){

        //use regex to check if the string has any ther character except 0 or 1

        if(a.matches("[01]+")){

            int length = a.length();

            BigInteger b = BigInteger.ONE.shiftLeft(length + 1);

            String c = b.add(new BigInteger(a, 2).not()).toString(2);

            c = c.substring(c.length() - length);

            return c;

        }

        //throw  exception for any such number

        throw new IllegalArgumentException ("Not a valid binary number");

    }

    public static void main(String args[])

    {

        //uncomment to check other test casses

        System.out.println(onesComplement("1000"));

        // System.out.println(onesComplement("0001"));

        // System.out.println(onesComplement("102"));

    }

    

}

Output
For Input : onesComplement("1000")

Solution 3

This is a direct exception handling question. use try/catch blocks while calling the methods .

Code

public class PositiveNumberStatistics {

    

    //private memer variable

    private double numbers[];

    //constructor

    PositiveNumberStatistics(double num[]){

        //if array has no elements throw exception

        if(num.length==0)

            throw new IllegalArgumentException("Array length of zero");

        else{

            numbers=new double[num.length];

            for(int i=0;i<num.length;i++){

                if(num[i]<=0)

                    throw new NumberFormatException("Non-positive value at index "+i);

                else{

                    numbers[i]=num[i];

                }

            }

        }

    }

    //function to return the average of values in the private member variable

    public double average(){

        double sum=0;

        for(int i=0;i<numbers.length;i++){

            sum = sum + numbers[i];

        }

        return sum/numbers.length;

    }

    public static void main(String args[]){

        //test case 1

        try{

            double val[]={5,8};

            PositiveNumberStatistics p=new PositiveNumberStatistics(val);

            System.out.println("Average of {5,8} : "+p.average());

        }

        catch(Exception e){

            System.out.println("Average of {5,8} Exception : "+e.toString());

        }

        //test case 2

        try{

            double val[]={};

            PositiveNumberStatistics p=new PositiveNumberStatistics(val);

            System.out.println("Average of {} : "+p.average());

        }

        catch(Exception e){

            System.out.println("Average of {} Exception : "+e.toString());

        }

        //test case 3

        try{

            double val[]={5,-1};

            PositiveNumberStatistics p=new PositiveNumberStatistics(val);

            System.out.println("Average of {5,-1} : "+p.average());

        }

        catch(Exception e){

            System.out.println("Average of {5,-1} Exception : "+e.toString());

        }

    

    }

}

Output: