java HashMap<String, Object> 如何替换对象的 1 个值？
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HashMap<String, Object> How to replace 1 value of the Object?
提问by user1621988
Map<String, Data> map = new HashMap<String,Data>();
map.put("jan", new Data("RED","M4A1",5,0,0));
How can I change the value RED of the Data object?, without getting all the information out of the map with the key and putting it back in, like this:
如何更改 Data 对象的值 RED？，而无需使用键从地图中取出所有信息并将其放回原处，如下所示：
map.put("jan" new Data("Blue",
map.get("jan").Brand,
map.get("jan").Storage,
map.get("jan").Sold,
map.get("jan").Bought));
So how can i change 1 value of the Data Object instead of redo them all?
那么如何更改数据对象的 1 个值而不是全部重做？
回答by Jon Skeet
It depends on whether Datais mutable. For example, you may be able to write:
这取决于是否Data可变。例如，您可以编写：
Data data = map.get("jan");
data.setColor("Blue");
Don't forget that the map only contains a referenceto the object, so if you change the data within the object, that change will be seen if someone fetches the reference from the map later.
不要忘记地图只包含对对象的引用，因此如果您更改对象内的数据，那么如果稍后有人从地图中获取引用，则会看到该更改。
Or if it's immutable, it could potentially have a withColormethod, so you could write:
或者如果它是不可变的，它可能有一个withColor方法，所以你可以写：
Data data = map.get("jan");
map.put("jan", data.withColor("Blue"));
Without knowing more about your Datatype (which I hope isn't the real name of your class) it's hard to say any more.
如果不了解您的Data类型（我希望这不是您班级的真实姓名），就很难再多说了。
(I also hope your class doesn't really have Pascal-cased fields, and I hope those fields are private, but that's a different matter...)
（我也希望你的班级没有真正的 Pascal-cased 字段，我希望这些字段是私有的，但那是另一回事......）
回答by Brian
Assuming Datais mutable you can set the "RED"field:
假设Data是可变的，您可以设置该"RED"字段：
Map map = new HashMap();
map.put("jan", new Data("RED","M4A1",5,0,0));
// Later...
map.get("jan").setColor("BLUE");
If Dataisn't mutable, then your only option is to putthe new value as you have it written.
如果Data不是可变的，那么您唯一的选择就是使用put您编写的新值。
回答by Jo?o Silva
Assuming Datahas a setterfor the colorproperty:
假设Data有一setter对color属性：
public class Data {
private String color;
public void setColor(String color) {
this.color = color;
}
}
You can just getthe required Dataobject and set its property:
您可以只get需要所需的Data对象并设置其属性：
Data data = map.get("jan");
data.setColor("blue");
回答by AlexR
Add appropriate setter to your Dataclass, e.g.
将适当的 setter 添加到您的Data类中，例如
class Data {
setColor(String color){...}
}
map.get("jan").setColor("BLUE");
回答by Shreyos Adikari
Please find the code snippet:
请找到代码片段：
Map<String, Data> map = new HashMap<String,Data>();
public class Data{
private String color;
public void setColor(String color) {
this.color = color;
}
public String getColor() {
return this.color;
}
publicData(String color){
this.setColor(color);
}
}
map.put("jan", new Data("RED","M4A1",5,0,0));
Now you may do like this:
现在你可以这样做：
Data data = map.get("jan");
data.setColor("black");
This will work.
这将起作用。
Here the class Data contains only one field i.e. color. You can add more fields. Thanks
这里的类 Data 只包含一个字段，即颜色。您可以添加更多字段。谢谢
