// references/Immutable2.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.
// A companion class to modify immutable objects

class Mutable {
 private int data;
 Mutable(int initVal) {
 data = initVal;
 }
 public Mutable add(int x) {
 data += x;
 return this;
 }
 public Mutable multiply(int x) {
 data *= x;
 return this;
 }
 public Immutable2 makeImmutable2() {
 return new Immutable2(data);
 }
}

public class Immutable2 {
 private int data;
 public Immutable2(int initVal) {
 data = initVal;
 }
 public int read() { return data; }
 public boolean nonzero() {
 return data != 0;
 }
 public Immutable2 add(int x) {
 return new Immutable2(data + x);
 }
 public Immutable2 multiply(int x) {
 return new Immutable2(data * x);
 }
 public Mutable makeMutable() {
 return new Mutable(data);
 }
 public static
 Immutable2 modify1(Immutable2 y) {
 Immutable2 val = y.add(12);
 val = val.multiply(3);
 val = val.add(11);
 val = val.multiply(2);
 return val;
 }
 // This produces the same result:
 public static
 Immutable2 modify2(Immutable2 y) {
 Mutable m = y.makeMutable();
 m.add(12).multiply(3).add(11).multiply(2);
 return m.makeImmutable2();
 }
 public static void main(String[] args) {
 Immutable2 i2 = new Immutable2(47);
 Immutable2 r1 = modify1(i2);
 Immutable2 r2 = modify2(i2);
 System.out.println("i2 = " + i2.read());
 System.out.println("r1 = " + r1.read());
 System.out.println("r2 = " + r2.read());
 }
}
/* Output:
i2 = 47
r1 = 376
r2 = 376
*/