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The Java Interview Handbook: 300+ Interview Questions

Finalize

Explore the deprecation of the finalize() method in Java introduced with JDK 9. Understand why this method should be avoided and how it impacts object lifecycle management and future Java releases.

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1.

Explain the finalize() method

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Java
import java.util.HashSet;
class Demonstration {
  
    static HashSet<UsefulObjectClass> immortals = new HashSet<>();  
  
    public static void main( String args[] ) throws InterruptedException {
        UsefulObjectClass obj = new UsefulObjectClass(immortals);
        obj.printName();
        obj = null;
        Runtime.getRuntime().gc();
        // Sleep the main thread so that the garbage collector thread performs finalization
        Thread.sleep(1000);
        if (immortals.size() == 1) {
            System.out.println("Useful object saved from garbage collection.");
        }
        System.out.println("exiting");      
    }
}
class UsefulObjectClass {
    HashSet<UsefulObjectClass> immortals;
    public UsefulObjectClass(HashSet<UsefulObjectClass> immortals) {
        this.immortals = immortals;
    }
    @Override
    public void finalize() {
        System.out.println("I am being finalized.");
        immortals.add(this);
    }
    public void printName() {
        System.out.println("Hi, I am a useful object.");
    }
}
1.

How many times does JVM invoke the finalize() method on an object?

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With the release of JDK 9 finalize() has been deprecated. Deprecation does not necessarily mean removal or future removal. It is an indication used to note that the annotated element should (if possible) be avoided and may potentially be removed in future releases of the Java platform.