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 segmentsSnake(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:es2 = :a:b:c:d:es2==s ? falses2.c==s.c ? trues2.next==s.next ? trueafter s.increments2.c==s.c ? falses2.next==s.next ? trueafter s.increment, s2 = :a:c:d:e:fafter s.increment, s = :b:c:d:e:f
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