如何确定从Java中的文本文件读入的最大值和最小值

Question

我正在上课的作业，正在寻找一些有用的指示，而不是完整的解决方案。 基本上，我必须编写一个Java程序，该程序读取一个文本文件并逐行列出信息，列出行号，最后打印出最大值和最小值以及与每个值相关的年份。 文本文件包含一年和该年的温度。 因此，它列出了类似“ 1900 50.9”的内容。 我不是要使用数组或扫描仪，这是分配的一部分。 我已经能够成功地使程序逐行打印，并逐行打印相应的温度。 有人告诉我，我确实使用了while循环。 现在，我唯一的问题是访问文本文件的方式可以以某种方式区分所有温度，即最高和最低，以及每年发生的年份。到目前为止，我一直没有寻求帮助。因为我希望自己能解决这个问题，但是由于罚款较晚，因此该作业不再值得任何荣誉。 任何帮助将不胜感激，因为我仍然想解决这个问题。 谢谢。

这就是我所拥有的。

public class main {

/**
 * @param args the command line arguments
 */

public static void main(String[] args) throws Exception {


File temps = new File ("temps.txt"); //Creates path to temps.txt file
FileReader textReader = new FileReader (temps); //Input information from temps.txt file into file reader
BufferedReader kb = new BufferedReader (textReader); //Use buffered reader to hold temps.txt file info from the file reader




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


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


    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)

}




}

}

到目前为止的输出是这样的：

Line 0: Year 1900: Temp 50.9
Line 1: Year 1901: Temp 49
Line 2: Year 1902: Temp 49.7
Line 3: Year 1903: Temp 49.5
Line 4: Year 1904: Temp 47.1
Line 5: Year 1905: Temp 49.1

等等...

Line 99: Year 1999: Temp 52.7
BUILD SUCCESSFUL (total time: 0 seconds)

Answer 1

这是一种方法：

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);

Answer 2

您需要使用一些变量来跟踪最小和最大温度。
每次出现更高（更低）的温度时，您都要更新变量。

好的，从循环外的最高最大值和最低最小值开始。
一旦在回路内看到（较高）较低的温度，就可以调整无功功率。
循环后，您可以回顾一下。

Answer 3

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

用伪代码：

highest = -inf
lowest = inf

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

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

这是一个例子

假设您的数据集是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