package aboutclone;
/**
* JAVA克隆之浅复制(此例来源于《JAVA编程思想》)
* NOTES:
* 类里的基本类型(此例中是 Char c)是深复制,自定义(此例是Snake next)或混合类型(如HashMap,ArrayList等)是浅复制.
* 所以深复制时要自己写克隆代码克隆每一个自定义类型(此例是Snake next)或混合类型的字段.
*/
public class Snake implements Cloneable {
private Snake next;
private char c;
// Value of i == number of segments
Snake(int i, char x) {
c = x;
if(--i > 0)
next = new Snake(i, (char)(x + 1));
}
void increment() {
c++;
if(next != null)
next.increment();
}
public String toString() {
String s = ":" + c;
if(next != null)
s += next.toString();
return s;
}
public Object clone() {
Object o = null;
try {
o = super.clone();
} catch (CloneNotSupportedException e) {}
return o;
}
public static void main(String[] args) {
Snake s = new Snake(5, 'a');
System.out.println("s = " + s);
Snake s2 = (Snake)s.clone();
System.out.println("s2 = " + s2);
System.out.print("s2==s ? ");
System.out.println(s2==s); //false,有深复制基本类型Char,两对象的第一个字段Char不同,
//但第二个引用类型Snake是指向同一对象,下面的打印输出可以看出.
System.out.print("s2.c==s.c ? ");
System.out.println(s2.c==s.c);//这里深复制了基本类型Char c ,值都是'a',所以为true
System.out.print("s2.next==s.next ? ");
System.out.println(s2.next==s.next);//这里没有深复制自定类型Snake,复制的是引用,但都是指向同一对象,所以为true
s.increment();
System.out.println("after s.increment");
System.out.print("s2.c==s.c ? ");
System.out.println(s2.c==s.c); //false, s2.c=='a' , s.c=='b'
System.out.print("s2.next==s.next ? ");
System.out.println(s2.next==s.next); //true , 浅复制,还是指用同一对象
System.out.println(
"after s.increment, s2 = " + s2);
System.out.println(
"after s.increment, s = " + s);
}
}
输出如下:
s = :a:b:c:d:e
s2 = :a:b:c:d:e
s2==s ? false
s2.c==s.c ? true
s2.next==s.next ? true
after s.increment
s2.c==s.c ? false
s2.next==s.next ? true
after s.increment, s2 = :a:c:d:e:f
after s.increment, s = :b:c:d:e:f