OnJava8-Examples/housekeeping/TerminationCondition.java

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// housekeeping/TerminationCondition.java
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// <20>2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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// Using finalize() to detect an object that
// hasn't been properly cleaned up.
import onjava.*;
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class Book {
boolean checkedOut = false;
Book(boolean checkOut) {
checkedOut = checkOut;
}
void checkIn() {
checkedOut = false;
}
@Override
protected void finalize() {
if(checkedOut)
System.out.println("Error: checked out");
// Normally, you'll also do this:
// super.finalize(); // Call the base-class version
}
}
public class TerminationCondition {
public static void main(String[] args) {
Book novel = new Book(true);
// Proper cleanup:
novel.checkIn();
// Drop the reference, forget to clean up:
new Book(true);
// Force garbage collection & finalization:
System.gc();
new Sleep(1); // Delay
}
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}
/* Output:
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Error: checked out
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*/