。您所做的是将相同的向量分配给另一个变量：

之前：

 code> finished ------> [a，b，c，d] 

之后：

 完成------> [a，b，c，d] 
 ^ 
 | 
 finished_copy --- / 
 

这里是如何复制一个Vector的所有元素另一个：

  Vector< Allocated> finishedCopy = new Vector<>（finished）; 
 

或

  Vector< Allocated> finishedCopy = new Vector<>（）; 
 finishedCopy.addAll（finished）; 
 

然而，这将创建两个不同的向量，其中包含对相同已分配实例的引用。如果你想要的是这些对象的副本，那么你需要创建显式副本。没有做副本，改变第一个列表中对象的状态也会改变它在第二个列表中的状态，因为这两个列表都包含对同一个对象的引用。

请注意：

• 类别应以大写字母开头


• 变量不应包含下划线， be camelCased


• 不应再使用向量。 ArrayList应该是，因为Java 2.我们在Java 8。

I am copying a vector to another vector of same type.And modifying the copy vector but the original vector is also getting update I don't understand why?

Vector<allocated>finished_copy=new Vector<allocated>();
finished_copy=finished;

I am printing the value of original vector after and before modification

for(int k=0;k<finished.size();k++) {
        System.out.print(finished.elementAt(k).output);
        System.out.print(finished.elementAt(k).step);
        System.out.println();
}//some modification on finished_copy

And printing the original but both are different

Please help me in this

You're not doing any copy. All you're doing is assigning the same Vector to another variable:

Before:

finished ------> [a, b, c, d]

After:

finished ------> [a, b, c, d]
                 ^
                 |
finished_copy ---/

Here's how you would copy all the elements of a Vector into another one:

Vector<Allocated> finishedCopy = new Vector<>(finished);

or

Vector<Allocated> finishedCopy = new Vector<>();
finishedCopy.addAll(finished);

This, however, will create two different vectors containing references to the same Allocated instances. If what you want is a copy of those objects, then you need to create explicit copies. Without doing a copy, changing the state of an object in the first list will also change its state in the second one, since both lists contain references to the same ojects.

Note that:

• classes should start with an uppercase letter
• variables should not contain underscares, but be camelCased
• Vector should not be used anymore. ArrayList should be, since Java 2. We're at Java 8.