Java的：创建HashMaps这样的列表 [英] Java: create a list of HashMaps

问题描述

我试图创建的地图列表。在下面的code，我期待获得

I tried to create a list of maps. In the following code, I'm expecting to get

[{start=1,text=ye}, {start=2,text=no}]

不过，我只得到了

however, I only got

[{start=2,text=no}, {start=2,text=no}]

如何避免覆盖第一张地图？这里是我的code：

How to avoid overriding the first map? Here is my code:

HashMap mMap = new HashMap();
ArrayList list = new ArrayList();
list.add(new HashMap());
mMap.put("start",1);
mMap.put("text","yes");
list.add(mMap); 
mMap.put("start",2);
mMap.put("text","no");
list.add(mMap); 
System.out.println("Final result: " + list );

谢谢！

=====

至于谁从程序语言的背景（SAS）传来的Java学习者，我花了好几个小时来学习和试验数组列表，链表，地图，LinkedMap等---我coldn't得到它的工作。我不与我有限的知识，为什么不懂。现在，这些如下回答都是极好的！他们在Java中解释的很重要的数据结构，至少​​对我来说。

As a learner of Java who came from a procedure language background (SAS), I spent quite a few hours learning and experimenting ArrayList, LinkedList, Map, LinkedMap, etc--- I coldn't get it to work. And I don't understand why with my limited knowledge. Now, these following answers are all excellent! They explained very important data structure in Java, at least for me.

谢谢大家！！！！

推荐答案

您需要创建一个新的HashMap为每个项，而不是重用现有的之一。这将工作：

You need to create a new HashMap for every entry, instead of reusing the existing one. This would work:

HashMap mMap = new HashMap();
mMap.put("start",1);
mMap.put("text","yes");
list.add(mMap); 
mMap = new HashMap(); // create a new one!
mMap.put("start",2);
mMap.put("text","no");
list.add(mMap); 

此外，您还可以删除 list.add（新的HashMap（））; 作为，增加了一个空映射到列表中是从来没有填充的

also, you can remove the list.add(new HashMap()); as that adds an empty map to your list that is never populated.

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