Mega Code Archive
Go through a few gyrations to add cloning to your own class
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// : appendixa:AddingClone.java
// You must go through a few gyrations
// to add cloning to your own class.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import java.util.ArrayList;
import java.util.Iterator;
class Int2 implements Cloneable {
private int i;
public Int2(int ii) {
i = ii;
}
public void increment() {
i++;
}
public String toString() {
return Integer.toString(i);
}
public Object clone() {
Object o = null;
try {
o = super.clone();
} catch (CloneNotSupportedException e) {
System.err.println("Int2 can't clone");
}
return o;
}
}
// Inheritance doesn't remove cloneability:
class Int3 extends Int2 {
private int j; // Automatically duplicated
public Int3(int i) {
super(i);
}
}
public class AddingClone {
public static void main(String[] args) {
Int2 x = new Int2(10);
Int2 x2 = (Int2) x.clone();
x2.increment();
System.out.println("x = " + x + ", x2 = " + x2);
// Anything inherited is also cloneable:
Int3 x3 = new Int3(7);
x3 = (Int3) x3.clone();
ArrayList v = new ArrayList();
for (int i = 0; i < 10; i++)
v.add(new Int2(i));
System.out.println("v: " + v);
ArrayList v2 = (ArrayList) v.clone();
// Now clone each element:
for (int i = 0; i < v.size(); i++)
v2.set(i, ((Int2) v2.get(i)).clone());
// Increment all v2's elements:
for (Iterator e = v2.iterator(); e.hasNext();)
((Int2) e.next()).increment();
System.out.println("v2: " + v2);
// See if it changed v's elements:
System.out.println("v: " + v);
}
} ///:~
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