deathcondition.java

thinking in Java书中 的源代码

//: c04:DeathCondition.java
// From 'Thinking in Java, 2nd ed.' by Bruce Eckel
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
// Using finalize() to detect an object that 
// hasn't been properly cleaned up.

class Book {
  boolean checkedOut = false;
  Book(boolean checkOut) { 
    checkedOut = checkOut; 
  }
  void checkIn() {
    checkedOut = false;
  }
  public void finalize() {
    if(checkedOut)
      System.out.println("Error: checked out");
  }
}

public class DeathCondition {
  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();
  }
} ///:~