Checking to see if a reference can be cloned : Clone « Class « Java

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Java » Class » CloneScreenshots 
Checking to see if a reference can be cloned
Checking to see if a reference can be cloned
      

// : appendixa:CheckCloneable.java
// Checking to see if a reference can be cloned.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.

// Can't clone this because it doesn't override clone():
class Ordinary {
}

// Overrides clone, but doesn't implement Cloneable:

class WrongClone extends Ordinary {
  public Object clone() throws CloneNotSupportedException {
    return super.clone()// Throws exception
  }
}

// Does all the right things for cloning:

class IsCloneable extends Ordinary implements Cloneable {
  public Object clone() throws CloneNotSupportedException {
    return super.clone();
  }
}

// Turn off cloning by throwing the exception:

class NoMore extends IsCloneable {
  public Object clone() throws CloneNotSupportedException {
    throw new CloneNotSupportedException();
  }
}

class TryMore extends NoMore {
  public Object clone() throws CloneNotSupportedException {
    // Calls NoMore.clone(), throws exception:
    return super.clone();
  }
}

class BackOn extends NoMore {
  private BackOn duplicate(BackOn b) {
    // Somehow make a copy of b and return that copy.
    // This is a dummy copy, just to make the point:
    return new BackOn();
  }

  public Object clone() {
    // Doesn't call NoMore.clone():
    return duplicate(this);
  }
}

// You can't inherit from this, so you can't override
// the clone method as you can in BackOn:

final class ReallyNoMore extends NoMore {
}

public class CheckCloneable {

  public static Ordinary tryToClone(Ordinary ord) {
    String id = ord.getClass().getName();
    System.out.println("Attempting " + id);
    Ordinary x = null;
    if (ord instanceof Cloneable) {
      try {
        x = (Ordinary) ((IsCloneableord).clone();
        System.out.println("Cloned " + id);
      catch (CloneNotSupportedException e) {
        System.err.println("Could not clone " + id);
      }
    else {
      System.out.println("Doesn't implement Cloneable");
    }
    return x;
  }

  public static void main(String[] args) {
    // Upcasting:
    Ordinary[] ord = new IsCloneable()new WrongClone()new NoMore(),
        new TryMore()new BackOn()new ReallyNoMore()};
    Ordinary x = new Ordinary();
    // This won't compile; clone() is protected in Object:
    //! x = (Ordinary)x.clone();
    // Checks first to see if a class implements Cloneable:
    for (int i = 0; i < ord.length; i++)
      tryToClone(ord[i]);

  }
///:~


           
         
    
    
    
    
    
  
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