Java 中非原始变量之间按值赋值
private List<CourseGroupBean> courseGroups = new ArrayList<CourseGroupBean>();
...
courseGroups = getAlgorithmUtil().listCourses();
...
List<CourseGroupBean> courseGroupsTwo = courseGroups;
我知道，如果我执行第三行，它将把 courseGroups 的引用分配给 courseGroupsTwo，但我只想分配它的值。在 Java 中如何做到这一点？
编辑
我的意思是，当我在 courseGroupsTwo 中删除/添加对象时，它不能更改 courseGroups 中的任何内容。
private List<CourseGroupBean> courseGroups = new ArrayList<CourseGroupBean>();
...
courseGroups = getAlgorithmUtil().listCourses();
...
List<CourseGroupBean> courseGroupsTwo = courseGroups;
I know that if I do the third line it will assing the reference of courseGroups to courseGroupsTwo but I want to assign just the values of it. How to do that in Java?
EDIT
I mean, when I remove/add an object at courseGroupsTwo it musn't change anything at courseGroups.
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Java 本身不支持对象的按值复制，因此您必须自己执行此操作：
将执行
courseGroups的浅表复制，即它将创建一个包含与以下内容相同的对象的新列表：课程组。如果需要，您可以将ArrayList替换为更合适的List实现。如果您愿意，还可以使用
克隆。clone有点令人讨厌，因为您需要在克隆之后进行强制转换。强制转换通常很糟糕，因为它可能会引入运行时错误，而如果出现问题，上面的代码将生成编译时错误。Java doesn't natively support copy-by-value for Objects, so you have to do it yourself:
will perform a shallow copy of
courseGroups, i.e. it will create a new list that contains the same objects ascourseGroups. You can replaceArrayListwith a more appropriateListimplementation if required.You can also use
cloneif you like.cloneis a bit nasty because you need to do a cast after the clone. Casting is generally bad because it possibly introduces run-time errors, whereas the code above will generate compile-time errors if something is wrong.您需要对列表进行“深层复制”。请参阅此 StackOverflow 答案。
You need to do a 'deep copy' of the list. See this StackOverflow answer.
但不仅仅是调用 .clone()。根据下面的资源，您的类还必须实现 Cloneable 接口；否则，将抛出 CloneNotSupportedException：
http: //www.roseindia.net/java/example/java/util/clone-method-example-in-java.shtml
But there is more than just calling .clone(). According to this resource below, your class also must implement the interface Cloneable; otherwise, a CloneNotSupportedException is thrown:
http://www.roseindia.net/java/example/java/util/clone-method-example-in-java.shtml
调用构造函数
ArrayList(Collection)：Call constructor
ArrayList(Collection<? extends E>):