2017-04-16 10:18:21 -07:00
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// references/LocalCopy.java
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2021-01-31 15:42:31 -07:00
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// (c)2021 MindView LLC: see Copyright.txt
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2017-04-16 10:18:21 -07:00
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// Creating local copies with clone()
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class Duplo implements Cloneable {
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private int n;
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2017-05-01 14:33:10 -06:00
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Duplo(int n) { this.n = n; }
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2021-01-31 15:42:31 -07:00
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@Override public Duplo clone() { // [1]
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2017-04-16 10:18:21 -07:00
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try {
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return (Duplo)super.clone();
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} catch(CloneNotSupportedException e) {
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throw new RuntimeException(e);
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}
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}
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public int getValue() { return n; }
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public void setValue(int n) { this.n = n; }
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public void increment() { n++; }
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2021-01-31 15:42:31 -07:00
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@Override public String toString() {
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2017-04-16 10:18:21 -07:00
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return Integer.toString(n);
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}
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}
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public class LocalCopy {
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public static Duplo g(Duplo v) {
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// Passing a reference, modifies outside object:
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v.increment();
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return v;
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}
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public static Duplo f(Duplo v) {
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2021-01-31 15:42:31 -07:00
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v = v.clone(); // Local copy // [2]
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2017-04-16 10:18:21 -07:00
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v.increment();
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return v;
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}
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public static void main(String[] args) {
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Duplo a = new Duplo(11);
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Duplo b = g(a);
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// Reference equivalence, not object equivalence:
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System.out.println("a == b: " + (a == b) +
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"\na = " + a + "\nb = " + b);
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Duplo c = new Duplo(47);
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Duplo d = f(c);
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System.out.println("c == d: " + (c == d) +
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"\nc = " + c + "\nd = " + d);
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}
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}
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/* Output:
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a == b: true
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a = 12
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b = 12
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c == d: false
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c = 47
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d = 48
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*/
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