IST 297D Introduction to Application Programming Chapter 4 Problem Set. Name:

Transcription

1 IST 297D Introduction to Application Programming Chapter 4 Problem Set Name: 1. Write a Java program to compute the value of an investment over a number of years. Prompt the user to enter the amount of the initial investment, the rate of return, and the number of years. Use a while loop to control iterations. Print both the year and the current value of the investment on each line. (2 points) public class WhileLoopInvestmentProblem // Constructs an investment object from a starting balance and interest rate. // User starts off with $10,000 at a rate of 5 return over 2 years. final double INITIAL_BALANCE = 10000; final double RATE = 5; final double TARGET = 2 * INITIAL_BALANCE; double balance = INITIAL_BALANCE; System.out.print("Enter number of years: "); int nyears = in.nextint(); while (balance < TARGET) nyears++; double interest = balance * RATE / 100; balance = balance + interest; System.out.println("The investment doubled after " + nyears + " years."); 2. Repeat problem 1 this time using a for loop. (2 points) public class ForLoopInvestmentProblemJava

2 // This Program prints a table showing the growth of an investment. final double RATE = 5; final double INITIAL_BALANCE = 10000; double balance = INITIAL_BALANCE; System.out.print("Enter number of years: "); int nyears = in.nextint(); // Print the table of balances for each year for (int year = 1; year <= nyears; year++) double interest = balance * RATE / 100; balance = balance + interest; System.out.printf("%4d %10.2f\n", year, balance); 3. Write a Java program that uses nested for loops to print a multiplication table as shown below. The value of each cell should be computed using the values in the row and column headings (eg 1 * 1; 1 * 2; 1 * 3; etc) (2 points) * // This program prints the multiplication powers from 1 to 9.

3 final int NMAX = 9; final double XMAX = 9; // Print table header for (int row = 1; row <= 9; row++) for (int col = 1; col <= 9; col++) //1..9 int product = row * col; if (product < 10 ) // a one-digit number System.out.print(" " + product + " "); else System.out.print(product + " "); System.out.println(""); 4. Write a Java program to calculate the average of a set of numbers (doubles) entered by the user. The user can enter as many numbers as they like. Use a do-while loop to control iterations. When the user enters a non-number, the program terminates and prints the average. (2 points) public class AverageSetOfNumbers // TODO code application logic here boolean valid = false; double fnum, snum, answer; while (!valid) System.out.println("Enter first num: "); fnum = in.nextdouble(); System.out.println("Enter second num: "); snum = in.nextdouble(); answer = fnum + snum; System.out.println(answer); if (fnum + snum <= ) valid = true; else if System.out.println("You entered a non-number"); System.out.println("My final value is: " +answer); else int counter = 0; do System.out.print(counter);

4 counter++; while(counter <= 30); System.out.println("My final value is: " +counter); 5. Write a program to generate random numbers between 1 and 100 in a user controlled loop. Use the Math.random() method to get the base number, but the number must be scaled to between 1 and 100. Prompt the user with Do you want a new number? If the user enters Yes generate and print the random number then prompt them again. If the user enters No the program terminates. If the user enters a string other than Yes or No prompt them with help to explain the legal entries. (2 points) package mathrandomproblem; import java.math.*; * ItalianRambo public class MathRandomProblem // User gets a random integer from 1 to 100. double randomnumber = 0; int randominteger = 0; String sentinel = "Y"; int count = 0; System.out.println("This program generates random numbers until you tell it to stop"); do System.out.print("Do you want a number (Y/N)? "); sentinel = in.next(); if(sentinel.equalsignorecase("y") sentinel.equalsignorecase("n")) if(sentinel.equalsignorecase("y")); randomnumber = Math.random(); randomnumber = randomnumber * 100; randominteger = (int) randomnumber;

5 randominteger = randominteger + 1; count++; System.out.println("Your number is "+randomnumber); System.out.println("Your integer is "+randominteger); else System.out.println("Y or N please!!!!!!"); sentinel = "Y"; while(sentinel.equalsignorecase("y")); System.out.print("Number of numbers generated: "+count);