Java 读取文本文件中的下一行
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/19595368/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Reading the next line in a text file
提问by coinbird
I'm trying to read input from a text file that will be formatted like this:
我正在尝试从文本文件中读取输入，该文件的格式如下：
2 80 97
5 69 79 89 99 58
7 60 70 80 90 100 0 59
The first number of each line is the number of "grades" per "section."
每行的第一个数字是每个“部分”的“等级”数。
I got my program to read one section, but I can't figure out how to make it read how many sections there will be, and then read the next line(s).
我让我的程序读取一个部分，但我不知道如何让它读取将有多少个部分，然后读取下一行。
I think I can put my current code in a count controlled loop that will first read how many sections there are, and run the loop that many times. I just don't know how to convert that idea to code.
我想我可以将我当前的代码放在一个计数控制循环中，该循环将首先读取有多少个部分，然后多次运行循环。我只是不知道如何将这个想法转换为代码。
Here is the revevant code section:
这是相关的代码部分：
public static void main(String args[]) throws Exception
{
Scanner in = new Scanner(new File("prog2test.txt"));
//int sections = (in.nextInt());
int scores = (in.nextInt());
int scoresForAverage = scores;
int scoreTotals = 0;
double average = 0;
int A = 0;
int B = 0;
int C = 0;
int D = 0;
int F = 0;
int highest = 0;
int lowest = 100;
while (scores > 0 && in.hasNextInt())
{
int grade = in.nextInt();
if (grade >= 90)
A++;
else if (grade >= 80)
B++;
else if (grade >= 70)
C++;
else if (grade >= 60)
D++;
else
F++;
if (grade > highest)
highest = grade;
if (grade < lowest)
lowest = grade;
scores--;
scoreTotals = (scoreTotals + grade);
}
average = scoreTotals/scoresForAverage;
System.out.println("Scores for section 1");
System.out.println("A's: " + A);
System.out.println("B's: " + B);
System.out.println("C's: " + C);
System.out.println("D's: " + D);
System.out.println("F's: " + F);
System.out.println("Lowest score: " + lowest);
System.out.println("Highest score: " + highest);
System.out.println("Average: " + average);
EDIT: Updated with complete method.
编辑：用完整的方法更新。
采纳答案by Embattled Swag
Since you know the first int in each line ISNT a grade, you can save each line using someString = in.nextLine()while in.hasNextLine()and then iterate over each saved string skipping the first integer using a new Scannerinstance for each line.
由于您知道每行中的第一个 int 不是一个等级，因此您可以使用someString = in.nextLine()while保存每一行in.hasNextLine()，然后使用Scanner每行的新实例遍历每个保存的字符串，跳过第一个整数。
回答by Arash Saidi
If you are using Scanner, you can use the method hasNext();
如果您使用的是 Scanner，则可以使用 hasNext() 方法；
This will be true as long as there are any strings in the text separated by a whitespace.
只要文本中有任何由空格分隔的字符串，就会出现这种情况。
回答by nhgrif
You can read the entire line, then use the String.splitmethod to split this into an array using a space delimiter.
您可以读取整行，然后使用该String.split方法使用空格分隔符将其拆分为一个数组。
After you read the line:
在你阅读这行之后：
String grades[] = line.split(" ");
Then you can use a forloop as such...
然后你可以使用一个for循环......
for(int i=1; i<grades.length; ++i) {
//start an index 1 to skip the non-grade first number on line
int grade = parseInt(grades[i]);
if (grade >= 90)
A++;
//etc on down the line
}
And contain this entire process in a whileloop to iterate over every line.
并将整个过程包含在while循环中以迭代每一行。
