do i need call close() on every new inputstream?

Question

here is the code.

public static void main(String[] args) throws IOException {

    FileInputStream fis = null;

    fis = new FileInputStream(new File("D:\\za180s.ser"));
    // do something
    fis = new FileInputStream(new File("D:\\za185s.ser"));
    // do something
    fis = new FileInputStream(new File("D:\\za186s.ser"));
    // do something
    fis = new FileInputStream(new File("D:\\za187s.ser"));
    // do something
    fis.close();

}

the problem is : need i call fis.close() method after every "do something" or i just call fis.close() once after all.

ignore whether the close() position in finally and the code need try catch or not.

thx all.

Yes, they all need to be closed. You could use Java's try-with-resources (https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html) to not have to manually close your inputstreams. — nbokmans, Mar 11 '19 at 09:12
Yes, you need to close them. You can use automatic resource management i.e. `try with resources` feature of Java 7 — AbhiN, Mar 11 '19 at 09:15
The answers below (correctly) say that you do need to close it, but they haven't explained *why*. In general, not closing input streams can lead to [resource exhaustion](https://en.wikipedia.org/wiki/Resource_exhaustion_attack). — Andy Turner, Mar 11 '19 at 09:17
because it is some fragment code from old project of company, it offen crash because “out of memory”. it needs refactoring optimization — nori, Mar 11 '19 at 09:17

score 10 · Answer 1 · answered Mar 11 '19 at 09:13

Yes, you need to call close on each individual InputStream. The problem with your code is that you're reassigning the variable fis each time you create a new stream. In other words: fis no longer points to the old InputStream, so calling close will not close the previous stream.

For more information, check https://stackoverflow.com/a/40523/8819761

What you could also do is use Java 7's try-with-resources syntax, which will auto-close the stream once you exit the try block:

try (InputStream fis = new FileInputSteam(yourFile)) {
  // Do something
}

try (InputStream fis = new FileInputSteam(yourFile)) {
  // Do something else
}

thanks ! old project of company, base on java6. leader won't let me to update the jdk on production environment. — nori, Mar 11 '19 at 09:20

score 0 · Answer 2 · answered Mar 11 '19 at 09:14

You have to do close everytime you finish working with InputStream.

In java, if you assign

 fis = new FileInputStream(new File("D:\\za180s.ser"));

fis will point to the new object so when you call fis.close() the old streams are not affected. And there is no way to close it.

score 0 · Answer 3 · answered Mar 11 '19 at 10:39

You need to call close method every time but don't worry now.From Java SE 7 you can use try-with-resources. As per Java-Oracle Doc,

The try-with-resources statement is a try statement that declares one or more resources. A resource is an object that must be closed after the program is finished with it. The try-with-resources statement ensures that each resource is closed at the end of the statement. Any object that implements java.lang.AutoCloseable, which includes all objects which implement java.io.Closeable, can be used as a resource.

Please have a look on example.

static String readFirstLineFromFile(String path) throws IOException {
    try (BufferedReader br =
                   new BufferedReader(new FileReader(path))) {
        return br.readLine();
    }
}

In this example, the resource declared in the try-with-resources statement is a BufferedReader. The declaration statement appears within parentheses immediately after the try keyword. The class BufferedReader, in Java SE 7 and later, implements the interface java.lang.AutoCloseable. Because the BufferedReader instance is declared in a try-with-resource statement, it will be closed regardless of whether the try statement completes normally or abruptly (as a result of the method BufferedReader.readLine throwing an IOException).

For more details, Please have a look on Oracle-Java doc for try-with-resources.

https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

do i need call close() on every new inputstream?

3 Answers3