//: appendixa:LocalCopy.java
// Creating local copies with clone().
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import com.bruceeckel.simpletest.*;
import java.util.*;

class MyObject implements Cloneable {
  private int n;
  public MyObject(int n) { this.n = n; }
  public Object clone() {
    Object o = null;
    try {
      o = super.clone();
    } catch(CloneNotSupportedException e) {
      System.err.println("MyObject can't clone");
    }
    return o;
  }
  public int getValue() { return n; }
  public void setValue(int n) { this.n = n; }
  public void increment() { n++; }
  public String toString() { return Integer.toString(n); }
}

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