...
This example creates a new file, outputs some text to it, and abruptly exits using Runtime.exit(). Consequently, the file is closed without the text actually being written to it.
| Code Block | ||
|---|---|---|
| ||
public class CreateFile {
public static void main(String[] args) throws FileNotFoundException {
final PrintStream out = new PrintStream( new BufferedOutputStream(
new FileOutputStream("foo.txt")));
out.println("hello");
Runtime.getRuntime().exit(1);
}
}
|
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This solution explicitly closes the file before exiting
| Code Block | ||
|---|---|---|
| ||
public class CreateFile {
public static void main(String[] args) throws FileNotFoundException {
final PrintStream out = new PrintStream( new BufferedOutputStream(
new FileOutputStream("foo.txt")));
out.println("hello");
out.close();
Runtime.getRuntime().exit(1);
}
}
|
...
This compliant solution adds a shutdown hook to close the file. This hook is invoked by Runtime.exit() is called before the JVM is halted.
| Code Block | ||
|---|---|---|
| ||
public class CreateFile {
public static void main(String[] args) throws FileNotFoundException {
final PrintStream out = new PrintStream( new BufferedOutputStream(
new FileOutputStream("foo.txt")));
Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
public void run() {
out.close();
}
}));
out.println("hello");
Runtime.getRuntime().exit(1);
}
}
|
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This noncompliant code example calls Runtime.halt() instead of Runtime.exit(). Runtime.halt() stops the JVM without invoking any shutdown hooks; consequently the file is not properly written to or closed.
| Code Block | ||
|---|---|---|
| ||
public class CreateFile {
public static void main(String[] args) throws FileNotFoundException {
final PrintStream out = new PrintStream( new BufferedOutputStream(
new FileOutputStream("foo.txt")));
Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
public void run() {
out.close();
}
}));
out.println("hello");
Runtime.getRuntime().halt(1);
}
}
|
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