Java 克隆学习的一个例子分析

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