48 lines
1.2 KiB
Java
48 lines
1.2 KiB
Java
//: references/LocalCopy.java
|
|
// Creating local copies with clone().
|
|
import java.util.*;
|
|
|
|
class MyObject implements Cloneable {
|
|
private int n;
|
|
public MyObject(int n) { this.n = n; }
|
|
@Override
|
|
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++; }
|
|
@Override
|
|
public String toString() { return Integer.toString(n); }
|
|
}
|
|
|
|
public class LocalCopy {
|
|
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);
|
|
}
|
|
} ///:~
|