A method to clone any clonable object.

  • By Steve Ball
  • September 12, 2000
EFFECTIVE JAVA
Enhancing container classes with deep-copy semantics
Steve Ball
Listing 1. A method to clone any clonable object.


public class GeneLab {
  public static Object clone(Object obj) {
    if (obj == null) return null;

    try {
      // use the Clonable interface if the object implements it
      return ((Clonable) obj).clone();
    } catch (ClassCastException e) {}

    // handle wrapper types and other immutable classes
    if (obj instanceof Boolean)    return obj; 
    if (obj instanceof Character)  return obj;
    if (obj instanceof Number)     return obj;
    if (obj instanceof String)     return obj;

    Class objClass = obj.getClass();

    try {
      // try accessing public clone method using reflection
      return objClass.getMethod("clone", null).invoke(obj, null);
    } catch (Exception e) {}

    try {
      // try accessing copy constructor using reflection
      Class[] params = new Class[] { objClass };
      Object[] args = new Object[] { obj };
      return objClass.getConstructor(params).newInstance(args);
    } catch (Exception e) {}

    // handle known classes as special cases
    if (obj instanceof java.util.Date)
      return new java.util.Date(((java.util.Date) obj).getTime());
    throw new CannotCloneObjectException();     // give up
  }

  private GeneLab() {}
}
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