java.util.NoSuchElementException: No line found

问题

I got an run time exception in my program while I am reading a file through a Scanner.

java.util.NoSuchElementException: No line found     
   at java.util.Scanner.nextLine(Unknown Source)    
   at Day1.ReadFile.read(ReadFile.java:49)  
   at Day1.ParseTree.main(ParseTree.java:17)

My code is:

while((str=sc.nextLine())!=null){
    i=0;
    if(str.equals(\"Locations\"))
    {
        size=4;
        t=3;
        str=sc.nextLine();
        str=sc.nextLine();
    }
    if(str.equals(\"Professions\"))
    {
        size=3;
        t=2;
        str=sc.nextLine();
        str=sc.nextLine();
    }
    if(str.equals(\"Individuals\"))
    {
        size=4;
        t=4;
        str=sc.nextLine();
        str=sc.nextLine();
    }

int j=0;
String loc[]=new String[size];
while(j<size){
    beg=0;
    end=str.indexOf(\',\');
    if(end!=-1){
        tmp=str.substring(beg, end);
        beg=end+2;
    }
    if(end==-1)
    {
        tmp=str.substring(beg);
    }
    if(beg<str.length())
        str=str.substring(beg);
    loc[i]=tmp;
    i++;

    if(i==size ){
        if(t==3)
        {
            location.add(loc);
        }
        if(t==2)
        {
            profession.add(loc);
        }
        if(t==4)
        {
            individual.add(loc);
        }
        i=0;
    }
    j++;
    System.out.print(\"\\n\");
}

回答1:

with Scanner you need to check if there is a next line with hasNextLine()

so the loop becomes

while(sc.hasNextLine()){
    str=sc.nextLine();
    //...
}

it's readers that return null on EOF

ofcourse in this piece of code this is dependent on whether the input is properly formatted

回答2:

You're calling nextLine() and it's throwing an exception when there's no line, exactly as the javadoc describes. It will never return null

http://download.oracle.com/javase/1,5.0/docs/api/java/util/Scanner.html

回答3:

For whatever reason, the Scanner class also issues this same exception if it encounters special characters it cannot read. Beyond using the hasNextLine() method before each call to nextLine(), make sure the correct encoding is passed to the Scanner constructor, e.g.:

Scanner scanner = new Scanner(new FileInputStream(filePath), "UTF-8");

回答4:

Your real problem is that you are calling "sc.nextLine()" more times than the number of lines.

For example, if you have only 10 input lines, then you can only call "sc.nextLine()"10 times.

Every time you call "sc.nextLine()", one input line will be consumed. If you call "sc.nextLine()" more times than the number of lines, you will have an exception called "java.util.NoSuchElementException: No line found".

If you have to call "sc.nextLine()" n times, then you have to have at least n lines.

Try to change your code to match the number of times you call "sc.nextLine()" with the number of lines, and I guarantee that your problem will be solved.

回答5:

I also encounter with that problem. In my case the problem was that i closed the scanner inside one of the funcs..

public class Main 
{
	public static void main(String[] args) 
	{
		Scanner menu = new Scanner(System.in);
        boolean exit = new Boolean(false);
    while(!exit){
		String choose = menu.nextLine();
        Part1 t=new Part1()
        t.start();
	    System.out.println("Noooooo Come back!!!"+choose);
		}
	menu.close();
	}
}

public class Part1 extends Thread 
{
public void run()
  { 
     Scanner s = new Scanner(System.in);
     String st = s.nextLine();
     System.out.print("bllaaaaaaa\n"+st);
     s.close();
	}
}

The code above made the same exaption, the solution was to close the scanner only once at the main.

回答6:

Need to use top comment but also pay attention to nextLine(). To eliminate this error only call

sc.nextLine()

Once from inside your while loop

 while (sc.hasNextLine()) {sc.nextLine()...}

You are using while to look ahead only 1 line. Then using sc.nextLine() to read 2 lines ahead of the single line you asked the while loop to look ahead.

Also change the multiple IF statements to IF, ELSE to avoid reading more than one line also.

来源：https://stackoverflow.com/questions/7209110/java-util-nosuchelementexception-no-line-found

标签

java

java.util.scanner