推 risker760915:所以說n維陣列就要在第n-1維的地方做clone(),這樣嗎? 05/03 18:27
→ risker760915:疑,好像還要看是基本型態的陣列還是物件陣列... 05/03 18:29
→ mars90226:或者可以直接deep clone 05/03 18:48
→ soso0316:好有深度XD...我在想一下 謝謝 05/04 00:21
陣列的 clone() 用的是 Object.clone()
而以下是 Object.clone() 的說明:
The method clone for class Object performs a specific cloning operation.
First, if the class of this object does not implement the interface
Cloneable, then a CloneNotSupportedException is thrown. Note that all arrays
are considered to implement the interface Cloneable and that the return type
of the clone method of an array type T[] is T[] where T is any reference or
primitive type. Otherwise, this method creates a new instance of the class of
this object and initializes all its fields with exactly the contents of the
corresponding fields of this object, as if by assignment; the contents of the
fields are not themselves cloned. Thus, this method performs a "shallow copy"
of this object, not a "deep copy" operation.
太多字不想看的話看標亮黃色的那一句就好:
它做的是 shallow copy 也就是每個成員直接指定過去而已
由於 Java 的多維陣列是陣列的陣列
因此 clone 一個 int[][] 只會開一個新的 int[][] 物件
然後把裡面每個 int[] 給指定過去
所以在你的例子裡 即使 b = a.clone(); 了
但 b[0] 和 a[0] 卻是指到同樣的一個一維陣列
這就造成你看到的現象了
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