java 如何在java中动态创建新变量
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/5537363/
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
How to create new variable in java dynamically
提问by ihavprobs
Is it possible to create new variables in java dynamically.
是否可以在java中动态创建新变量。
class A {
methodA(String variableName) {
}
}
So if new method is called twice, 2 new variables should be newly added to this class?
那么如果新方法被调用两次，那么这个类应该新添加2个新变量吗？
Is it possible?
是否可以？
回答by Jon Skeet
No. Have you considered storing a Map<String, Object>in the class instead? The keys in the map would be the "variable names" and the values in the map would be the logical variable names.
不。你有没有考虑过Map<String, Object>在类中存储 a ？映射中的键是“变量名”，映射中的值是逻辑变量名。
If you could give more information about what you're trying to achieve (from a high-level perspective) that would help.
如果你能提供更多关于你想要实现的目标的信息（从高层次的角度），那会有所帮助。
回答by aioobe
No, this is not possible to do in Java.
不，这在 Java 中是不可能的。
The fields in a class is determined at compile time and can't be changed during runtime (except though sophisticated techniques such as class reloading though for instance JRebel). I would however not recommend doing this, unless you're writing some IDE for instance.
类中的字段在编译时确定，不能在运行时更改（除非使用复杂的技术，例如类重新加载，例如JRebel）。但是，我不建议这样做，除非您正在编写一些 IDE。
回答by Ben
A class and its members are defined and then compiled to bytecode, so they cannot be readily modified at run-time. That said, there are a number of libraries out there, such as cglib, which provide runtime modification functionality. This page can tell you more: http://java-source.net/open-source/bytecode-libraries
定义类及其成员，然后编译为字节码，因此在运行时不能轻易修改它们。也就是说，有许多库，例如 cglib，它们提供运行时修改功能。这个页面可以告诉你更多：http: //java-source.net/open-source/bytecode-libraries
(This is not to say that runtime modification is the right thing to do!)
（这并不是说运行时修改是正确的做法！）
回答by slezica
In a good design, a class must represent something, semantically speaking. You design it to represent an object in your system.
在一个好的设计中，从语义上讲，一个类必须代表一些东西。你设计它来代表你系统中的一个对象。
If you want to add more things to a design in run-time, well, something's not quite right -- unless, of course, the design needs adding information in run-time, and there are tons of data structures just ready for the job!
如果您想在运行时向设计添加更多内容，那么有些事情不太正确——当然，除非设计需要在运行时添加信息，并且有大量数据结构已准备就绪！
Check out Maps in Java, for example.
Map例如，检查Java 中的 s。
回答by gmhk
Following is the way that i have implemented and helped me to fix my solution easily without much hurdles.
以下是我实施并帮助我轻松解决我的解决方案的方式，没有太多障碍。
// Creating the array List
// 创建数组列表
List accountList = new ArrayList();
for(int k=0;k < counter;k++){
accountList.add(k, (String)flowCtx.getValueAt("transitId"+m));
}
Iterating the loop and adding the objects into the arraylist with the index.
迭代循环并将对象添加到带有索引的数组列表中。
//Retrieving the object at run time with the help of the index
//在运行时借助索引检索对象
String a = accountList.get(i));
回答by Capensis
Using a HashMap could be a solution. For example, if we have the following class:
使用 HashMap 可能是一个解决方案。例如，如果我们有以下类：
class Staff {
private HashMap<String, Object> mylist = new HashMap<String, Object>() ;
void setNewVar(String s, Object o) {
mylist .put(s, o);
}
HashMap<String, Object> getVar() {
return mylist;
}
}
I can use it as:
我可以将它用作：
staff.setNewVar("NumVars",11);
staff.setNewVar("NumBatches",300);
...
and then:
接着：
staff.getVar()
wherever you need. I use it to convert some variables (the number can change) to JSON, successfully.
无论您需要什么。我用它成功地将一些变量（数字可以改变）转换为 JSON。
