java try finally block to close stream
In Java 7 you can do this...
try (BufferedReader r = new BufferedReader(...)){
String inLine;
while ((inLine = r.readLine()) != null) {
System.out.println(inLine);
}
} catch(IOException e) {
//handle exception
}
- Declaring a variable in the try block requires that it implements
AutoCloseable
. - Declaring a variable in the try block also limits its scope to the try block.
- Any variable declared in the try block will automatically have
close()
called when the try block exits.
It's called a Try with resources statement.
It seems a bit clunky.
It is. At least java7's try with resources fixes that.
Pre java7 you can make a closeStream
function that swallows it:
public void closeStream(Closeable s){
try{
if(s!=null)s.close();
}catch(IOException e){
//Log or rethrow as unchecked (like RuntimException) ;)
}
}
Or put the try...finally inside the try catch:
try{
BufferedReader r = new BufferedReader(new InputStreamReader(address.openStream()));
try{
String inLine;
while ((inLine = r.readLine()) != null) {
System.out.println(inLine);
}
}finally{
r.close();
}
}catch(IOException e){
e.printStackTrace();
}
It's more verbose and an exception in the finally will hide one in the try but it's semantically closer to the try-with-resources introduced in Java 7.
Also if you're using Java 7, you can use a try-with-resources statement:
try(BufferedReader r = new BufferedReader(new InputStreamReader(address.openStream()))) {
String inLine;
while ((inLine = r.readLine()) != null) {
System.out.println(inLine);
}
} catch(IOException readException) {
readException.printStackTrace();
}