why this warning in this java program

Question

i need help i am getting error like

Description                               Resource        Path                Location    Type  
Resource leak: 'input' is never closed    Methods.java    /piyush/src/piyush  line 7      Java Problem

Code:

import java.util.Scanner;
public class Methods {


 public static void main(String[] args){
   Scanner input = new Scanner(System.in);
   System.out.print("what is your name ");
   String yourName = input.nextLine();
   System.out.println("hello " + yourName);
 }


 }

I think message is clear. What part of *'input' is never closed* you don't understand? — m0skit0, Dec 26 '14 at 14:16

score 4 · Accepted Answer · answered Dec 26 '14 at 14:14

4

You should close streams after their use. In your case, add

input.close();

just after the last System.out.println() to close your Scanner and get rid of the warning.

answered Dec 26 '14 at 14:14

Spikatrix

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In fact he should close in a `finally` block. – m0skit0 Dec 26 '14 at 14:18
@m0skit0 Yes, then he uses a Java version from the dark ages. [The try-with-resources Statement](http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html). – Tom Dec 26 '14 at 14:23
1

@m0skit0, You mean in a `try{...}finally{input.close();}`? – Spikatrix Dec 26 '14 at 14:26
what if i have to use later scanner will it work? – noob programmer Dec 26 '14 at 14:56
@PiyushKashyap , No. You've freed whatever resources it was consuming. You'll have to create a new `Scanner`. Also,read the first sentence of my answer. – Spikatrix Dec 26 '14 at 14:59
@Tom Java 6 is most popular version (because of Android mostly) – m0skit0 Dec 26 '14 at 18:39

Mustafa sabir · Answer 2 · 2014-12-26T14:27:01.280

2

Its not a error, its a warning. Errors/Exceptions are if there is some mistake in your code (compilation errors) or if something goes wrong while execution of program (runtime exceptions).

You should always close streams that you use, in your case Scanner input:-

input.close();

This warning can be ignored and it should work fine without the close() , but it is a good practice to close resources after usage.

edited Dec 26 '14 at 14:27

answered Dec 26 '14 at 14:21

Mustafa sabir

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score 0 · Answer 3 · answered Dec 26 '14 at 14:16

0

You need to close the scanner to release any system resources. Use

input.close();

as the last line in your code. See Closeable.close() javadoc for some more info.

answered Dec 26 '14 at 14:16

Aleks G

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He should close in a `finally` block to be more correct. – m0skit0 Dec 26 '14 at 14:18
@m0skit0 Yes, that would be the correct way of doing it - but really he needs to add proper error handling anyway. – Aleks G Dec 26 '14 at 14:20

M A · Answer 4 · 2014-12-26T14:25:29.370

0

You can close the Scanner and it would be fine in this case, but this will close the underlying System.in input stream and prevent you from accepting input in case you later read from the standard input stream.

edited Dec 26 '14 at 14:25

answered Dec 26 '14 at 14:16

M A

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1

Whats wrong with closing the underlying input stream ? – Mustafa sabir Dec 26 '14 at 14:17
1

If he has no more use of Scanner, he should close it, not ignore the warning. – m0skit0 Dec 26 '14 at 14:17
1

Fixing errors tends to be a lot more effective than suppressing/ignoring them. – David Dec 26 '14 at 14:21
1

@Mustafasabir Closing `System.in` won't allow the user to accept input after closing the scanner. – M A Dec 26 '14 at 14:22
@manouti I don't see he's going to use it any more in the posted code. – m0skit0 Dec 26 '14 at 18:40
1

@m0skit0 Yes, hence the "in case" in the answer. – M A Dec 26 '14 at 18:50

why this warning in this java program

4 Answers4