Java - 关闭扫描程序和资源泄漏 [英] Java -- Closing Scanner and Resource Leak

问题描述

我正在学习Java，并在一些项目上开展工作。我遇到的一个问题是，当我使用 Scanner 对象时，Eclipse会警告我：

资源泄漏：'scan'永远不会关闭。

所以，我添加了一个 scan.close（）; 在我的代码的末尾，并且处理警告。

问题出在，因为我在同一个软件包中还有其他类也使用扫描器对象，而且Eclipse会告诉我分别关闭这些类的扫描程序。但是，当我这样做时，它似乎关闭了所有的扫描仪对象，并在运行时得到错误。

以下是导致错误原因的示例：

  import java.util.Scanner的; 
 public class test2 {
 public static void main（String [] args）{
扫描仪扫描=新的扫描仪（System.in）; 
 int test = 0; 
 do {
 // Do stuff 
 test = scan.nextInt（）; 
 System.out.println（test）; 
 
 scanTest scanTest = new scanTest（）; 
 scanTest.test（）; 
} while（test！= 0）; 
 
 scan.close（）; 
} 
} 
 
 import java.util.Scanner; 
 public class scanTest {
 public void test（）{
扫描仪扫描仪=新的扫描仪（System.in）; 
 int blah = scanner.nextInt（）; 
 System.out.println（blah）; 
 scanner.close（）; 
} 
} 
  

扫描仪关闭后，$ code > scanTest 类，并且 test2 中的do循环再次输入错误发生在行$ test = scan.nextInt ）;

我尝试将扫描器对象的创建移动到do循环中，以便每次都创建一个新对象，但错误仍然发生

不知道为什么会发生这种情况，或者我如何确保我的所有I / O对象在没有遇到问题的情况下关闭。

我发现一个帖子提到，当$ code> System.in 关闭时，我无法重新打开。如果是这样，我只需要确保在System.in的扫描仪对象在程序的最后关闭，并且@suppress其他类中的所有其他扫描仪警告？或者是否仍然将所有扫描仪对象打开（坏）？

解决方案

是的，当您关闭扫描仪时，您将关闭底层流（在这种情况下为System.in）。为了避免这种情况，可以创建扫描仪的全局变量，可以由所有类使用，也可以有一个中心点来关闭扫描仪（在程序退出之前就是理想的）

I'm learning Java and working on some projects for fun. One issue that I have run in to is that when I use a Scanner object Eclipse warns me that:

Resource Leak: 'scan' is never closed.

So, I added a scan.close(); at the end of my code and that takes care of the warning.

The problem comes in because I have other classes in the same package that also use scanner objects and and Eclipse tells me to close scanner in those classes respectively. However, when I do that it seems like it closes ALL of the scanner objects and I get errors during run time.

Here is an example of what causes the error:

import java.util.Scanner;
public class test2 {
    public static void main(String [] args) {
        Scanner scan = new Scanner(System.in);
        int test = 0;
        do {    
            //Do stuff
            test = scan.nextInt();
            System.out.println(test);

            scanTest scanTest = new scanTest();
            scanTest.test();
        } while (test != 0);

        scan.close();       
    }
}

import java.util.Scanner;
public class scanTest { 
    public void test() {
        Scanner scanner = new Scanner(System.in);
        int blah = scanner.nextInt();
        System.out.println(blah);
        scanner.close();
    }
}

After scanner is closed in the scanTest class and the do loop in test2 is entered again an error occurs at the line test = scan.nextInt();

I tried moving the creation of the scanner object into the do loop just to make a new object every time as well but the error still occurs.

Not sure why this is happening or how I can make sure all my I/O objects are closed out without running into problems.

One post I came across mentioned that when System.in is closed I cannot be re-opened. If this is the case would I just need to make sure a scanner object with System.in is closed at the very end of the program and @suppress all of the other scanner warnings in other classes? Or would that still leave all those scanner objects open (bad)?

解决方案

Yes, when you close a scanner you will be closing the underlying stream (in this case System.in). To avoid this, either create a global variable of scanner which can be used by all classes or have a central point for shutting down the scanner (just before the program exits would be ideal)

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