Java Programming

Finding Maximum and Minimum Values

A common task that must be done in a loop is to find the maximum and minimum of a sequence of values. The file Temps.java contains a program that reads in a sequence of hourly temperature readings over a 24-hour period. You will be adding code to this program to find the maximum and minimum temperatures. Do the following:

1. Save the file to your directory, open it and see whats there. Note that a for loop is used since we need a count-controlled loop. Your first task is to add code to find the maximum temperature read in. In general to find the maximum of a sequence of values processed in a loop you need to do two things:

You need a variable that will keep track of the maximum of the values processed so far. This variable must be initialized before the loop. There are two standard techniques for initialization: one is to initialize the variable to some value smaller than any possible value being processed; another is to initialize the variable to the first value processed. In either case, after the first value is processed the maximum variable should contain the first value. For the temperature program declare a variable maxTemp to hold the maximum temperature. Initialize it to -1000 (a value less than any legitimate temperature).

The maximum variable must be updated each time through the loop. This is done by comparing the maximum to the current value being processed. If the current value is larger, then the current value is the new maximum. So, in the temperature program, add an if statement inside the loop to compare the current temperature read in to maxTemp.

If the current temperature is larger set maxTemp to that temperature. NOTE: If the current temperature is NOT larger, DO NOTHING!

2. Add code to print out the maximum after the loop. Test your program to make sure it is correct. Be sure to test it on at least three scenarios: the first number read in is the maximum, the last number read in is the maximum, and the maximum occurs somewhere inthe middle of the list. For testing purposes you may want to change the HOURSPERDAY

variable to something smaller than 24 so you dont have to type in so many numbers!

3. Often we want to keep track of more than just the maximum. For example, if we are finding the maximum of a sequence of test grades we might want to know the name of the student with the maximum grade. Suppose for the temperatures we want to keep track of the time

(hour) the maximum temperature occurred. To do this we need to save the current value of the hour variable when we update the maxTemp variable. This of course requires a new variable to store the time (hour) that the maximum occurs. Declare timeOfMax (type int) to

keep track of the time (hour) the maximum temperature occurred. Modify your if statement so that in addition to updating maxTemp you also save the value of hour in the timeOfMaxvariable. (WARNING: you are now doing TWO things when the if condition is TRUE.)

4. Add code to print out the time the maximum temperature occurred along with the maximum.

5. Finally, add code to find the minimum temperature and the time that temperature occurs. This idea is the same as for the maximum. NOTE: Use a separate if when updating the minimum temperature variable (that is, dont add an else clause to the if that is already there).

// ************************************************************

// Temps.java

//

// This program reads in a sequence of hourly temperature

// readings (beginning with midnight) and prints the maximum

// temperature (along with the hour, on a 24-hour clock, it

// occurred) and the minimum temperature (along with the hour

// it occurred).

// ************************************************************

import java.util.Scanner;

public class Temps

{

// --------------------------------------------------

// Reads in a sequence of temperatures and finds the

// maximum and minimum read in.

// --------------------------------------------------

public static void main (String[] args){

final int HOURS_PER_DAY = 24;

int temp; // a temperature reading

Scanner scan = new Scanner(System.in);

// print program heading

System.out.println ();

System.out.println ("Temperature Readings for 24 Hour Period");

System.out.println ();

for (int hour = 0; hour < HOURS_PER_DAY; hour++){

System.out.print ("Enter the temperature reading at " + hour + " hours: ");

temp = scan.nextInt();

}

//prints the result

}

}