Question

我正在为一个班级做一个家庭作业，我正在寻找一些有用的指针，而不是完整的解决方案。基本上，我必须编写一个Java程序，该程序读入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。文本文件包含该年份和该年份的温度。因此，它列出了类似“1900 50.9”的内容。我不打算使用数组或扫描仪，这是作业的一部分。我已经能够成功地使程序每年打印出来，并且相应的温度与行数一致。我被告知，并使用了while循环。现在，我唯一的问题是以某种方式访问文本文件，我可以在某种程度上区分所有温度，这是最大值，哪个是最小值，以及每个温度发生在哪一年。我到目前为止还没有寻求帮助因为我希望能够自己解决这个问题，但由于迟到的惩罚，这项任务不再值得任何信任。任何帮助都会非常感激，因为我仍然想解决这个问题。感谢。

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：

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。一直到......

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，都会更新变量。

好的，从循环外的极高和最低分钟开始一旦在循环内看到（较高的）较低温度，就会调整变量循环后你回顾一下。

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

在伪代码中：

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

如何确定从Java中的文本文件读入的最大值和最小值

3 个答案: