How to Determine the Max and Min Values Read in From a Text File in Java

Question

I am doing a homework assignment for a class, and am looking for some helpful pointers, not full solutions. Basically, I have to write a Java program that reads in a text file a

Answer 1

Highest Seen So Far: -Infinity
    (or any really low number so that any number you see next will be higher)
Lowest Seen So Far: Infinity
    (or any really high number so that any number you see next will be lower)

Walk through each data point "d":
    is d higher than your latest "highest seen so far"?
        -> if yes, your new highest seen so far is now d
    is d lower than your latest "lowest seen so far"?
        -> if yes, your new lowest seen so far is now d

Your highest seen so far is now the highest data point
Your lowest seen so far is now the lowest data point

In pseudocode:

highest = -inf
lowest = inf

for d in dataset:
  if d > highest:
    highest = d
  if d < lowest:
    lowest = d

print "highest: " + highest
print "lowest: " + lowest

here is an example

let's say your dataset is 5 2 8 4

Step 0
    Highest: -inf
    Lowest: inf

Step 1
  See d = 5...that's higher than highest -inf, so new highest is 5.
  See d = 5...that's lower than lowest -inf, so new lowest is 5
    Highest: 5
    Lowest: 5

Step 2:
  See d = 2...that's not higher than highest 5...highest is still 5
  See d = 2...that is lower than lowest 5...new lowest is 2
    Highest: 5
    Lowest: 2

Step 3:
  See d = 8...that's higher than highest 5...new highest is 8
  See d = 8...that's not lower than lowest 2...lowest is still 2
    Highest: 8
    Lowest: 2

Step 4:
  See d = 4...that's not higher than highest 8...highest is still 8
  See d = 4...that's not lower than lowest 2...lowest is still 2
    Highest: 8
    Lowest: 2

Result:
    Highest: 8
    Lowest: 2

Answer 2

You need to use a few variables to keep track of the min and max temp.
Every time a higher (lower) temp comes along you update the variables.

Ok start with very high max and very low min outside the loop.
As soon as you see a (higher) lower temp inside the loop you adjust the vars.
After the loop you recap.

Answer 3

Here is a way to do it:

String tempList; //Create string variable named tempList
int lineCount = 0; //Create integer variable named lineCount
String sep = ": Temp "; //Create string variable named sep (short for separation) and set it equal to the literal string ":"
String space = " "; //Create string variable named space and set it equal to an actual space between texts

String maxValueYear = "";
String minValueYear = "";
double maxValue = 0;
double minValue = Double.MAX_VALUE;
System.out.println("The following is the provided information from the file input. ");
while ((tempList = kb.readLine()) !=null) { //while loop stating that as long as the text file still has values to read (is not null), continue to execute

    String year = tempList.substring(0, tempList.indexOf(space));
    double temp = Double.valueOf(tempList.substring(tempList.indexOf(space), tempList.length()));

    if (temp > maxValue) {
        maxValue = temp;
        maxValueYear = year;
    }
    if (temp < minValue) {
        minValue = temp;
        minValueYear = year;
    }
    System.out.println("Line " + lineCount++ + ": Year " + tempList.replace(space, sep)); //Prints out the line number (lineCount++), the info from the temps.txt file with a ":" between the year and the number (tempList.replace (space,sep)

}

System.out.println("The minimum temp occured in year " + minValueYear + " and was " + minValue);
System.out.println("The maximum temp occured in year " + maxValueYear + " and was " + maxValue);