// references/LocalCopy.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Creating local copies with clone()

class Duplo implements Cloneable {
 private int n;
 Duplo(int n) { this.n = n; }
 @Override
 public Duplo clone() { // [1]
 try {
 return (Duplo)super.clone();
 } catch(CloneNotSupportedException e) {
 throw new RuntimeException(e);
 }
 }
 public int getValue() { return n; }
 public void setValue(int n) { this.n = n; }
 public void increment() { n++; }
 @Override
 public String toString() {
 return Integer.toString(n);
 }
}

public class LocalCopy {
 public static Duplo g(Duplo v) {
 // Passing a reference, modifies outside object:
 v.increment();
 return v;
 }
 public static Duplo f(Duplo v) {
 v = v.clone(); // [2] Local copy
 v.increment();
 return v;
 }
 public static void main(String[] args) {
 Duplo a = new Duplo(11);
 Duplo b = g(a);
 // Reference equivalence, not object equivalence:
 System.out.println("a == b: " + (a == b) +
 "\na = " + a + "\nb = " + b);
 Duplo c = new Duplo(47);
 Duplo d = f(c);
 System.out.println("c == d: " + (c == d) +
 "\nc = " + c + "\nd = " + d);
 }
}
/* Output:
a == b: true
a = 12
b = 12
c == d: false
c = 47
d = 48
*/