in java

$6\mathrm{.}18($Displaying a Square of Asterisks$)$Write a method squareOfAsterisks that displays a solid square $($the same number of rows and columns$)$ of asterisks whose side is specified in integer parameter side. For example, if side is $4,$ the method should display

$****$

$****$

$****$

$****$

Incorporate this method into an application that reads an integer value for side from the user and outputs the asterisks with the squareOfAsterisks method.

$6\mathrm{.}19($Displaying a Square of Any Character$)$Modify the method created in Exercise $6\mathrm{.}18$ to receive a second parameter of type char called fillCharacter. Form the square using the char provided as an argument. Thus, if side is $5$ and fillCharacter is #$,$ the method should display

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Use the following statement $($in which input is a Scanner object$)$ to read a character from the user at the keyboard:

$//$ next$()$ returns a String and charAt$(0)$ gets the String$$s first character

char fill $=$ input.next$().$charAt$(0)$;

$6\mathrm{.}20($Circle Area$)$ Write an application that prompts the user for the radius of a circle and uses a method called circleArea to calculate the area of the circle.

$6\mathrm{.}21($Separating Digits$)$Write methods that accomplish each of the following tasks:

Calculate the integer part of the quotient when integer a is divided by integer b$.$

Calculate the integer remainder when integer a is divided by integer b$.$

Use the methods developed in parts $($a$)$ and $($b$)$ to write a method displayDigits that receives an integer between $1$ and $99999$ and displays it as a sequence of digits, separating each pair of digits by two spaces. For example, the integer $4562$ should appear as

$4562$

Incorporate the methods into an application that inputs an integer and calls displayDigits by passing the method the integer entered. Display the results.

$6\mathrm{.}22($Temperature Conversions$)$Implement the following integer methods:

Method celsius returns the Celsius equivalent of a Fahrenheit temperature, using the calculation

celsius $=5\mathrm{.}0/9\mathrm{.}0*($fahrenheit $-32)$;

Method fahrenheit returns the Fahrenheit equivalent of a Celsius temperature, using the calculation

fahrenheit $=9\mathrm{.}0/5\mathrm{.}0*$ celsius $+32$;

Use the methods from parts $($a$)$ and $($b$)$ to write an application that enables the user either to enter a Fahrenheit temperature and display the Celsius equivalent or to enter a Celsius temperature and display the Fahrenheit equivalent.

$6\mathrm{.}23($Find the Minimum$)$Write a method minimum$3$ that returns the smallest of three floating$-$point numbers. Use the Math.min method to implement minimum$3.$ Incorporate the method into an application that reads three values from the user, determines the smallest value and displays the result.

$6\mathrm{.}24($Perfect Numbers$)$ An integer number is said to be a perfect number if its factors, including $1($but not the number itself$),$ sum to the number. For example, $6$ is a perfect number, because $6=1+2+3.$ Write a method isPerfect that determines whether parameter number is a perfect number. Use this method in an application that displays all the perfect numbers between $1$ and $1000.$ Display the factors of each perfect number to confirm that the number is indeed perfect. Challenge the computing power of your computer by testing numbers much larger than $1000.$ Display the results.

$6\mathrm{.}25($Prime Numbers$)$A positive integer is prime if it$$s divisible by only $1$ and itself. For example, $2,3,5$ and $7$ are prime, but $4,6,8$ and $9$ are not. The number $1,$ by definition, is not prime.

Write a method that determines whether a number is prime.

Use this method in an application that determines and displays all the prime numbers less than $10,000.$ How many numbers up to $10,000$ do you have to test to ensure that you$$ve found all the primes?

Initially, you might think that n$/2$ is the upper limit for which you must test to see whether a number n is prime, but you need only go as high as the square root of n$.$ Rewrite the program, and run it both ways.

$6\mathrm{.}26($Reversing Digits$)$ Write a method that takes an integer value and returns the number with its digits reversed. For example, given the number $7631,$ the method should return $1367.$ Incorporate the method into an application that reads a value from the user and displays the result.

$6\mathrm{.}27($Greatest Common Divisor$)$ The greatest common divisor $($GCD$)$ of two integers is the largest integer that evenly divides each of the two numbers. Write a method gcd that returns the greatest common divisor of two integers. $[$Hint: You might want to use Euclid$$s algorithm. You can find information about it at en$.$wikipedia.org$/$wiki$/$Euclidean$\_$algorithm.$]$ Incorporate the method into an application that reads two values from the user and displays the result.

$6\mathrm{.}28$ Write a method qualityPoints that inputs a student$$s average and returns $4$ if it$$s $90100,3$ if $8089,2$ if $7079,1$ if $6069$ and $0$ if lower than $60.$ Incorporate the method into an application that reads a value from the user and displays the result.