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# jGrasp assistance/Java Using Loops

Problem 5.2 Using a Sentinel Value to control a while Loop

On this exercise I need to write a while loop that uses a sentinel value to control a loop in a Java program. I also need to write the statements that make up the body of the loop. I have already entered the necessary variable declarations and output statements.
• Each theater patron enters a value from 0 to 4 indicating the number of stars that the patron awards to the Guide's featured movie of the week. The program executes continuously until the theater manager enters a negative number to quit.
• I need to write the while loop using a sentinel value to control the loop, and also write the statements that make up the body of the loop.

import javax.swing.JOptionPane;

public class MovieGuide
{
public static void main(String args[])
{

// Declare and initialize variables.
double numStars; // star rating.
String numStarsString; // string version of star rating
double averageStars; // average star rating.
double totalStars = 0; // total of star ratings.
int numPatrons = 0; // keep track of number of patrons

// This is the work done in the housekeeping() method
// Get input.

// This is the work done in the detailLoop() method
// Convert to double.

// Write while loop here

// This is the work done in the endOfJob() method
// Calculate average star rating

System.out.println("Average Star Value: " + averageStars);

System.exit(0);
} // End of main() method.

} // End of MovieGuide class.

Problem 5.3 Using a for Loop

After I have completed this program it should print the numbers 0 through 10, along with their values multiplied by 10 and by 100.
• I need to write a for loop that uses the loop control variable to take on the values 0 through 10.
• In the body of the loop, multiply the value of the loop control variable multiplied by 10 and by 100.

public class NewMultiply
{
public static void main(String args[])
{

String head2 = "Multiplied by 10: ";
String head3 = "Multiplied by 100: ";
int numberCounter; // Numbers 0 through 10.
int byTen; // Stores the number multiplied by 10.
int byHundred; // Stores the number multiplied by 100.
final int NUM_LOOPS = 10; // Constant used to control loop.

// This is the work done in the housekeeping() method
System.out.println("0 through 10 multiplied by 10 and by 100" + "n");

// This is the work done in the detailLoop() method
// Write for loop

// This is the work done in the endOfJob() method
System.exit(0);
} // End of main() method.

} // End of NewMultiply class.

Problem 5.6 Accumulating Totals in a Loop
After I have completed this program, it should calculate two totals: the number of left-handed people and the number of right-handed people in your class. The loop should execute until the user enters the character 'X' instead of a 'L' for left-handed or 'R' for right-handed.
Left or Right-Handed
L
R
R
R
L
L
R
X

• I need to write a loop and a loop body that allows you to calculate a total of left-handed and a total of right-handed people in our class.
// LeftOrRight.java - This program calculates the total number of left-handed and right-handed
// students in a class.
// Input: L for left-handed; R for right handed; X to quit.
// Output: Prints the number of left-handed students and the number of right-handed students.

import javax.swing.JOptionPane;

public class LeftOrRight
{
public static void main(String args[])
{

String leftOrRight = ""; // L or R for one student.
int rightTotal = 0; // Number of right-handed students.
int leftTotal = 0; // Number of left-handed students.

// This is the work done in the housekeeping() method
leftOrRight = JOptionPane.showInputDialog("Enter L if you are left-handed, R if you are right-handed or X to quit.");

// This is the work done in the detailLoop() method

// This is the work done in the endOfJob() method
// Output number of left or right-handed students.
System.out.println("Number of left-handed students: " + leftTotal);
System.out.println("Number of right-handed students: " + rightTotal);
System.exit(0);
} // End of main() method.

} // End of LeftOrRight class.

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jGrasph assistance and Java using loops are examined.

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