Question

In java books and online tutorials it is stated that Object.clone() method provides shallow copying unless Cloneable interface is used but in the code I implemented clone() method without using Cloneable interface and it is providing a deep copy instead of a shallow copy.

import java.util.GregorianCalendar;
public class test1 {

   public static void main(String[] args) {

      // create a gregorian calendar, which is an object
      GregorianCalendar cal = new GregorianCalendar();

      // clone object cal into object y
      GregorianCalendar y = (GregorianCalendar) cal.clone();

      // check if reference of y is equal to cal or not
      System.out.println(cal==y);//it's output should be true if this is a shallow copy but it is false.
   }
}

Answer 1

GregorianCalendar确实实现了Cloneable接口，因此应该进行深层复制。

编辑：Java仅处理对对象的引用。因此，在这种情况下，由于GregorianCalendar的{{1}}方法执行了深复制，因此复制引用的一种方法是将clone分配给cal，即{ {1}}。

clone() method (Shallow or Deep copying)

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