Java Learning Note Scanner error java.util.NoSuchElementException

reprinted from: It learner-crab

A method a uses the scanner and closes it inside. Then after calling method A in method B, you can no longer use Scanner Scanner in = new Scanner (system.in);

The test code is as follows:

ImportJava.util.Scanner;/** * * @authorIt learner-crab * **/  Public classItxxzscanner {//First time input Public voidFisttime () {Scanner SC=NewScanner (system.in);intFirst =Sc.nextint (); System.out.println ("First:" +First ); Sc.close (); } //Second input Public voidSecondtime () {Scanner SC=NewScanner (system.in);intSecond =Sc.nextint (); System.out.println ("Second:" +second); Sc.close (); } //Test Portal Public Static voidMain (String arg[]) {Itxxzscanner T=NewItxxzscanner (); T.fisttime (); T.secondtime ();} } 

After running, the following exception is thrown:

As you can see, in the 29th line of code error, throw a java.util.NoSuchElementException exception,

Let's analyze the cause of the error:

1. Use Sc.close () in Fisttime () {...}, close processing, and turn off system.in.

2, when the next time in Secondtime () {...} When the new Scanner (system.in) operation is read in the method, the read value is 1 because the input stream is closed;

3, in the scanner Readinput method has the following code:

Try=catch==-1;} if (n = =-1truefalse;}

4, because read 1 on the set sourceclosed =true;neepinput=false;

5. The following code is in the next method:

if (Needinput) readinput (); Else throwfor ();

6, when the Needinput is false, the execution of throwfor, so look at throwfor

false ; if ((sourceclosed) && (position = = Buf.limit ())) Throw New nosuchelementexception (); Else Throw New

7, position is the current read content in the buffer position, because the read is 1, so position = 0, and Buf.limit () is also equal to 0, therefore executed the throw new Nosuchelementexception ();

Java Learning Note Scanner error java.util.NoSuchElementException