CODEWITHSUNDEEP
javabufferedreader
mahmood
mahmood

Reputation: 24705

BufferedReader proper usage

I use the following style to read a file with BufferedReader

try (BufferedReader br = new BufferedReader(new FileReader("my_file"))) {
  ...
  br.close();
} catch( IOException e ) {
  System.out.println( e.getMessage() );
}

Things that I want to know:

1- Is close() in the right place?

2- Should I put another try..catch for `close()?

3- Since I used new for br, is the enough to call the close() or I have to write br = null for the GC?

4- FileReader has been newed, so should I destroy it?

Upvotes: 3

Views: 1526

Answers (4)

Michael A. Schaffrath
Michael A. Schaffrath

Reputation: 2110

  1. Since you use the try-with-resource statement, you don't need to close the stream explicitely. It is automatically closed in any case. If you wouldn't have used try-with-resource, the close() would have been in the wrong place. To make sure your resource is always closed, you need to call close() in the finally block
  2. If you call close() in the finally block, you need to catch the checked Exception thrown by it, too. If you use try-with-resource (like you did), you are fine
  3. All your variables live only in the scope of the try block, so you are safe
  4. BufferedReader closes the decorated Reader, so you don't have to close it explicitely

Upvotes: 5

JEY
JEY

Reputation: 7123

you are using try-with-resources statement. You don't need to explicitly call close on your Reader. Indeed the documentation state:

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.

Furthermore your FileReader is Decorated by the BufferedReader and closing BufferedReader should close the FileReader.

Upvotes: 1

Ibrokhim Kholmatov
Ibrokhim Kholmatov

Reputation: 1089

You are using try-with-resources statement in you code. 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. You can learn more about this statement from documentation. So, here is modified version:

try (BufferedReader br = new BufferedReader(new FileReader("my_file"))) {
  // your logic

} catch (IOException e) {
  System.out.println(e.getMessage());
}

Upvotes: 2

shalama
shalama

Reputation: 1335

1-2- It is better to use close together with a finally or resource block. Otherwise the close will not get called if an Exception occurs before.

3- It is enough to call close(). Setting objects to null does not delete the reference. GC will destroy the objects when there are nor references to the objects anymore. So don't destroy your objects manually.

Upvotes: 0

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