我们的任务是检索文件并对其进行分类并将其显示在另一个文件中。姓氏名字，然后是成绩。
由于错误
，我遇到循环问题"java.util.NoSuchElementException"
只有在我循环播放时才更改当前存在的情况。我也有显示结果的问题。我显示的结果是一行，我不能发生。到目前为止，这是我的代码：
import java.util.*;
import java.util.StringTokenizer;
import java.io.*;
import javax.swing.*;
import java.text.DecimalFormat;
class Grade
{
public static void main(String [] args)throws IOException
{
//declaring
String line = "";
StringTokenizer st;
String delim = " \t\n\r,-";
String token;
String firstname;
String lastname;
String grade;
String S69andbelow="Students with 69 or below\n";
String S70to79 ="Students with 70 to 79\n";
String S80to89= "Students with 80 to 89\n";
String S90to100= "Students with 90 to 100\n";
int gradeint;
double gradeavg = 0;
int count = 0;
File inputFile = new File("input.txt");
File outputFile = new File("output.txt");
FileInputStream finput = new FileInputStream(inputFile);
FileOutputStream foutput = new FileOutputStream(outputFile);
FileReader reader = new FileReader(inputFile);
BufferedReader in = new BufferedReader(reader);
Scanner std = new Scanner(new File("input.txt"));
Scanner scanner = new Scanner(inputFile);
BufferedWriter out = new BufferedWriter(new FileWriter(outputFile));
Scanner scan = new Scanner(S69andbelow);
//reading linev
line = scanner.nextLine();
st = new StringTokenizer(line, delim);
//avoiding selected characters
try
{
while(st.hasMoreTokens())
{
firstname = st.nextToken(); //<----error started to happen
lastname = st.nextToken(); //here
grade = st.nextToken(); //and here
//storing tokens into their properties
gradeint = Integer.parseInt(grade);
//converting token to int
gradeavg = gradeavg + gradeint;
//calculating avg
count++;
//recording number of entries
if (gradeint <=69)
{
S69andbelow = S69andbelow + lastname + " "
+ firstname + " " + "\t" + grade + "\n";
} // saving data by grades
else if (gradeint >= 70 && gradeint <= 79)
{
S70to79 = S70to79 + lastname + " " + firstname
+ " " + "\t" + grade + "\n";
} // saving data by grades
else if (gradeint >= 80 && gradeint <=89)
{
S80to89 = S80to89 + lastname + " " + firstname
+ " " + "\t" + grade + "\n";
} // saving data by grades
else
{
S90to100 = S90to100 + lastname + " " + firstname
+ " " + "\t" + grade + "\n";
} // saving data by grades
}//end while
System.out.println(S69andbelow + "\n" + S70to79 + "\n"
+ S80to89 + "\n" + S90to100);
//caterorizing the grades
gradeavg = gradeavg / count;
//calculating average
DecimalFormat df = new DecimalFormat("#0.00");
out.write("The average grade is: "
+ df.format(gradeavg));
System.out.println("The average grade is: "
+ df.format(gradeavg));
Writer output = null;
output = new BufferedWriter(new FileWriter(outputFile));
// scanner.nextLine(S69andbelow);
//output.write(S69andbelow + "\n" + S70to79 + "\n"
// + S80to89 + "\n" + S90to100);
// output.close();
}
catch( Exception e )
{
System.out.println(e.toString() );
}
// Close the stream
try
{
if(std != null )
std.close( );
}
catch( Exception e )
{
System.out.println(e.toString());
}
}
}
问题已得到解答。最后的接触如下： / * ** * ** * ** * ** * ** * ** * 课程名称：年级 姓名：Dennis Liang 截止日期：2011年3月31日 程序描述：编写程序 从文件中读取列表 有成绩的学生。还显示 姓氏，名字，然后成绩。 的 * ** * ** * ** * ** * ** * **** /
import java.util。; import java.util.StringTokenizer; import java.io。; import javax.swing。*; import java.text.DecimalFormat;
班级 { public static void main（String [] args）抛出IOException
{
//declaring
String delim = " \t\n\r,-";
String token;
String firstName;
String lastName;
String grade;
String S69andbelow="Students with 69 or below\n";
String S70to79 ="Students with 70 to 79\n";
String S80to89= "Students with 80 to 89\n";
String S90to100= "Students with 90 to 100\n";
String all;
int gradeint;
double gradeavg = 0;
int count = 0;
int countTwo = 0;
File inputFile = new File("input.txt");
File outputFile = new File("output.txt");
FileInputStream finput = new FileInputStream(inputFile);
FileOutputStream foutput = new FileOutputStream(outputFile);
FileReader reader = new FileReader(inputFile);
BufferedReader in = new BufferedReader(reader);
Scanner std = new Scanner(new File("input.txt"));
Scanner scanner = new Scanner(inputFile);
BufferedWriter out = new BufferedWriter(new FileWriter(outputFile));
Scanner scan = new Scanner(S69andbelow);
try
{
String line, newLine = (String)System.getProperty("line.separator");
//seperating lines
while((line = in.readLine()) != null){
//Will only work if the file is properly formatted
StringTokenizer st = new StringTokenizer(line, " ");
if (st.countTokens() == 3)
{
firstName = st.nextToken();
lastName = st.nextToken();
grade = st.nextToken();
gradeint = Integer.parseInt(grade);
//retrieving tokens
gradeavg = gradeavg + gradeint;
//formula for avg
count++;
//avg count
//organizing by grades
if (gradeint <=69)
{
S69andbelow = S69andbelow + newLine+ lastName + " "
+ firstName + " " + "\t" + grade + newLine;
}
else if (gradeint >= 70 && gradeint <= 79)
{
S70to79 = S70to79 +newLine+ lastName + " " + firstName
+ " " + "\t" + grade + newLine;
}
else if (gradeint >= 80 && gradeint <=89)
{
S80to89 = S80to89 + newLine+ lastName + " " + firstName
+ " " + "\t" + grade + newLine;
}
else
{
S90to100 = S90to100 + newLine+ lastName + " " + firstName
+ " " + "\t" + grade + newLine;
}
} 其他{ countTwo ++; System.out.println（“有”+ countTwo +“人/人”+ “这需要额外的信息”+“\ n”）; } //通知用户有多少人 } //缺少信息或太多。
System.out.println(S69andbelow + "\n" + S70to79 + "\n"
+ S80to89 + "\n" + S90to100);
//caterorizing the grades
gradeavg = gradeavg / count;
//calculating average
DecimalFormat df = new DecimalFormat("#0.00");
//formating
System.out.println("The average grade is: "
+ df.format(gradeavg));
//displaying
Writer output = null;
output = new BufferedWriter(new FileWriter(outputFile));
//make file
output.write(newLine + S69andbelow + newLine + S70to79 + newLine
+ S80to89 + newLine + S90to100);
output.write("The average grade is: "
+ df.format(gradeavg));
//outputing to file
output.close();
//saving
}
catch（例外e）
{
System.out.println（e.toString（））;
}
//关闭流
尝试
{
if（std！= null）
std.close（）;
}
catch( Exception e )
{
System.out.println(e.toString());
}
} }
答案 0 :(得分：0)
每次调用st.nextToken（）之前都需要检查st.hasMoreTokens（）
就新行而言，Windows需要\ n \ 0
或者，您可以使用System.getProperty（“line.separator”），它为您提供每个操作系统的正确换行符。
String line, newLine = (String)System.getProperty("line.separator");
while((line = in.readLine()) != null){
//Will only work if the file is properly formatted
StringTokenizer st = new StringTokenizer(line, " ");
firstName = st.nextToken();
lastName = st.nextToken();
grade = st.nextToken();
gradeint = Integer.parseInt(grade);
gradeavg = gradeavg + gradeint;
count++;
if (gradeint <=69)
{
S69andbelow = S69andbelow + lastname + " "
+ firstname + " " + "\t" + grade + newLine;
}
else if (gradeint >= 70 && gradeint <= 79)
{
S70to79 = S70to79 + lastname + " " + firstname
+ " " + "\t" + grade + "\n";
}
else if (gradeint >= 80 && gradeint <=89)
{
S80to89 = S80to89 + lastname + " " + firstname
+ " " + "\t" + grade + newLine;
}
else
{
S90to100 = S90to100 + lastname + " " + firstname
+ " " + "\t" + grade + newLine;
}
}