在 Java 中复制向量中的向量
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/11414027/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Copy Vector in a Vector in Java
提问by researcher
I'd like to copy a vector to another. The problem is that if I change the vector v1, the second vector v2is changing too. My goal is to keep the copy intact even if I change the source vector.
我想将一个向量复制到另一个向量。问题是，如果我改变 vector v1，第二个 vectorv2也会改变。我的目标是即使更改源向量也能保持副本完整。
import java.util.Collections;
import java.util.Vector;
public class CopyElementsOfVectorToVectorExample {
public static void main(String[] args) {
//create first Vector object
Vector v1 = new Vector();
//Add elements to Vector
v1.add("1");
v1.add("2");
v1.add("3");
//create another Vector object
Vector v2 = new Vector(v1.size());
v2.setSize(v1.size());
Collections.copy(v2,v1);
System.out.println("After copy, Second Vector Contains : " + v2);
}}
How can I keep the second copy intact?
我怎样才能保持第二个副本完好无损？
回答by JB Nizet
Your code above is fine, although too complex. It could be reduced to
你上面的代码很好，虽然太复杂了。可以减少到
Vector copy = new Vector(original);
Also, you should avoid Vector, and use ArrayList instead.
此外，您应该避免使用 Vector，而使用 ArrayList。
回答by aioobe
[...] I change the vector v1, the second v2 is changing too ...My goal is to keep the copy intact even if I change the source vector ..
[...]我改变了向量 v1，第二个 v2 也在改变......我的目标是即使我改变源向量也能保持副本完整......
The vector contains referencesto objects. If you change the objects, then the change will be visible from both vectors.
该向量包含对对象的引用。如果您更改对象，则更改将从两个向量中都可见。
I believe what you're after is a deep copy.
我相信你所追求的是深拷贝。
回答by KingMaker
You can use Below code to clone a vector.
您可以使用下面的代码来克隆一个向量。
Vector v1 = new Vector();
//Add elements to Vector
v1.add("1");
v1.add("2");
v1.add("3");
//create another Vector object
Vector v2 = (Vector)v1.clone();
回答by amicngh
the problem is if I change the vector v1, the second v2 is changing too ...My goal is to keep the copy intact even if I change the source vector
the problem is if I change the vector v1, the second v2 is changing too ...My goal is to keep the copy intact even if I change the source vector
This is because Collections.copy(v2,v1)make a sallow copynot deep copy.
这是因为Collections.copy(v2,v1)赚了蜡黄复制不深拷贝。
Make deep copyof your Vector.
做深复制你的Vector。
Apologize for previous answer.
为之前的回答道歉。
Edit:
编辑：
I am assuming that your vectoris containing objects of type Serializable. With this approach you can get a deep copy of your collection.
我假设您vector包含类型为 的对象Serializable。通过这种方法，您可以获得收藏的深层副本。
static public Object deepCopy(Object oldObj) throws Exception {
ObjectOutputStream oos = null;
ObjectInputStream ois = null;
try {
ByteArrayOutputStream bos = new ByteArrayOutputStream(); // A
oos = new ObjectOutputStream(bos); // B
// serialize and pass the object
oos.writeObject(oldObj); // C
oos.flush(); // D
ByteArrayInputStream bin = new ByteArrayInputStream(
bos.toByteArray()); // E
ois = new ObjectInputStream(bin); // F
// return the new object
return ois.readObject(); // G
} catch (Exception e) {
System.out.println("Exception in ObjectCloner = " + e);
throw (e);
} finally {
oos.close();
ois.close();
}
}
