使用构造函数Java复制对象 [英] Copying an object using a constructor, Java

问题描述

所以我想说，我想做一个对象的深层副本，但使用它的contsructor。所以我有：

So lets say I want to make a deep copy of an object, but using its contsructor. So I have:

public class PositionList {
    private Position[] data = new Position[0];
    private int size = 0;

public PositionList(PositionList other, boolean deepCopy) {
    if (deepCopy==true){
        size=other.getSize();
        for (int i=0;i<data.length;i++)
        data[i]=other.data[i];
    }
    else {
        data=other.data;
        size = other.size;

所以说我有这个叫：

PositionList list = new PositionList();
PositionList acopy = new PositionList(list, true);

然而，我在做什么不正确，

What I am doing, however, is incorrect, and Im not sure why..

推荐答案

问题在于你的复制逻辑：

The problem lies in your deep copy logic:

size=other.getSize();
for (int i=0;i<data.length;i++)
    data[i]=other.data[i];

您正在设置 size 与数据数组是多余的），但是没有为数据字段指定一个新数组，这可能是整个点你的深副本。您应该将数据初始化为其他人的 size （或 other.data.length ）：

You are setting the size field (which is redundant with the data array) but are not assigning a new array to the data field, which is presumably the whole point of your "deep" copy. You should initialize data to the other's size (or other.data.length):

data = new Position[other.data.length];
for (int i=0;i<data.length;i++)
    data[i]=other.data[i];

（除掉 size ）

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