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From: Cecil Westerhof <Cecil@decebal.nl>
Newsgroups: comp.lang.java.programmer
Subject: What goes wrong with cloning here
Date: Fri, 23 Oct 2015 17:49:58 +0200
Organization: Decebal Computing
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Content-Type: text/plain

I need to use Cloneable. (I know that some people say you should never
use it, but it is a requirement of the project.)

I made something I thought should work, but it does not. I have
attached my dumbed down code. What am I doing wrong?

When I in class A change a field from class B in the clone, the field
in the original is also changed. That should not happen.


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Content-Type: text/x-java-source
Content-Disposition: attachment; filename=A.java

public class A implements Cloneable {
	private B key;

	private String c;
	private String d;

	public A() {
	}

	public Object clone() throws CloneNotSupportedException {
		A clone  = (A) super.clone();
		B newKey = new B();
        B oldKey = getKey();

		newKey.setA(oldKey.getA());
		newKey.setB(oldKey.getB());
		newKey.setC(oldKey.getC());
		newKey.setD(oldKey.getD());
		clone.setKey(key);

		return clone;
	}

	public String getC() {
		return c;
	}

	public String getD() {
		return d;
	}

	public B getKey() {
		return key;
	}

	public void setC(String c) {
		this.c = c;
	}

	public void setD(String d) {
		this.d = d;
	}

	public void setKey(B key) {
		this.key = key;
	}

    public static void main(String[] args) throws CloneNotSupportedException {
        A clone, original;
        B key;

        System.out.println("Got here");
        original = new A();
        key      = new B();
        key.setA("Some text");
        key.setB(12);
        key.setC(73);
        original.setKey(key);
        clone = (A) original.clone();
        clone.getKey().setB(99);
        System.out.println(original.getKey());
        System.out.println(clone.getKey());
    }

}

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Content-Type: text/x-java-source
Content-Disposition: attachment; filename=B.java

import java.io.Serializable;
import java.util.Date;

public class B implements Serializable {
	private static final long serialVersionUID = 1L;

	private String a;
	private int    b;
	private int    c;
	private Date   d;

	public B() {
	}

	public String getA() {
		return a;
	}

	public int getB() {
		return b;
	}

	public int getC() {
		return c;
	}

	public Date getD() {
		return d;
	}

	public void setA(String a) {
		this.a = a;
	}

	public void setB(int b) {
		this.b = b;
	}

	public void setC(int c) {
		this.c = c;
	}

	public void setD(Date d) {
		this.d = d;
	}

    public String toString() {
        return String.format("B [a: %s, b: %s, c: %s, d: %s]", a, b, c, d);
    }

}

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Content-Type: text/plain


-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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