Mega Code Archive
0130 Automatic Resource Management
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Java's try-with-resources statement automatically closes resources.
The try-with-resources statement consists of a try block:
try ([resource declaration; ...] resource declaration)
{
// code to execute
}
The following example uses try-with-resources:
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class Copy {
public static void main(String[] args) {
try {
copy("c:/a.txt", "c:/b.txt");
} catch (FileNotFoundException fnfe) {
String msg = "FileNotFoundException";
System.err.println(msg);
} catch (IOException ioe) {
String msg = "IOException";
System.err.println(msg);
}
}
static void copy(String srcFile, String dstFile) throws IOException
{
try (
FileInputStream fis = new FileInputStream(srcFile);
FileOutputStream fos = new FileOutputStream(dstFile)
)
{
int b;
while ((b = fis.read()) != -1)
fos.write(b);
}
}
}
A try-with-resources statement can include catch and finally. These blocks are executed after all declared resources have been closed.
To take advantage of try-with-resources, a resource class must implement the java.lang.AutoCloseable interface or its java.lang.Closeable subinterface.
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
class Main {
final static String LINE_SEPARATOR = "\n";
public static void main(String[] args) {
String dest = "a.hex";
try (FileInputStream fis = new FileInputStream(args[0]);
FileOutputStream fos = new FileOutputStream(dest)) {
} catch (IOException ioe) {
System.err.println("I/O error: " + ioe.getMessage());
}
}
}
The following code auto close a Socket connection.
import java.io.InputStream;
import java.net.Socket;
public class Main {
public static void main(String[] args) {
try (Socket socket = new Socket("yourTimeServer.com", 13)) {
InputStream is = socket.getInputStream();
int ch;
while ((ch = is.read()) != -1) {
System.out.print((char) ch);
}
} catch (Exception ioe) {
System.err.println("I/O error: " + ioe.getMessage());
}
}
}
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