根据Oracle的Javadoc，Object.clone()的通常惯例如下：

• x.clone() != x
• x.clone().getClass() == x.getClass()
• x.clone().equals(x)

通过调用super.clone()返回对象，可以帮助我们满足这些条件：

• super.clone() 返回一个新对象实例
• super.clone() 返回调用clone()方法相同类型的对象实例
• Object.clone() 为对象状态执行影子复制

比如，如下代码：

class BaseClass implements Cloneable {
  @Override
  public Object clone() throws CloneNotSupportedException {    // Non-Compliant - should return the super.clone() instance
    return new BaseClass();
  }
}

class DerivedClass extends BaseClass implements Cloneable {
  /* Does not override clone() */

  public void sayHello() {
    System.out.println("Hello, world!");
  }
}

class Application {
  public static void main(String[] args) throws Exception {
    DerivedClass instance = new DerivedClass();
    ((DerivedClass) instance.clone()).sayHello();              // Throws a ClassCastException because invariant #2 is violated
  }
}

应该重构为：

class BaseClass implements Cloneable {
  @Override
  public Object clone() throws CloneNotSupportedException {    // Compliant
    return super.clone();
  }
}

class DerivedClass extends BaseClass implements Cloneable {
  /* Does not override clone() */

  public void sayHello() {
    System.out.println("Hello, world!");
  }
}

class Application {
  public static void main(String[] args) throws Exception {
    DerivedClass instance = new DerivedClass();
    ((DerivedClass) instance.clone()).sayHello();              // Displays "Hello, world!" as expected. Invariant #2 is satisfied
  }
}