> using an object's attribute as key

I have an object Foo with the following elements:

class Foo {
    int id;
    int departmentId;
    boolean condition1;
    boolean condi,java,java-8"/>
	














    

		

        

            
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首页  > 解决方案 > 转换列表 into a Map> using an object's attribute as key

I have an object Foo with the following elements:



class Foo {
    int id;
    int departmentId;
    boolean condition1;
    boolean condi












java - 转换列表 into a Map> using an object's attribute as key

I have an object Foo with the following elements:



class Foo {
    int id;
    int departmentId;
    boolean condition1;
    boolean condi





问题描述



I have an object Foo with the following elements:



class Foo {
    int id;
    int departmentId;
    boolean condition1;
    boolean condition2;
    boolean condition3;
    //...
}




and a list of Foo objects (~10k entries):



List<Foo> fooList = new ArrayList<>();
fooList.add(...);
//...




I need to iterate through each of the departmentIds of this list, and be able to stop any further iterations of a particular departmentId once its objects meet a particular combination of conditions. 



For this purpose, I was thinking to simply create a new Map which holds my departmentId as a key and all related Foo objects as its value. So that I could iterate through my new objects based on the departmentId, and easily stop the iteration for other departments with same Id once the condition is met. Something like:



Map<Foo.departmentId, List<Foo>> departmentFoos = new HashMap<>();




Can this be achieved in a better way other than iterating through my fooList and putting/replacing the object of my HashMap one by one?







ElasticSearch/Kibana: The correct syntax to exclude a value?


I'm racking my brain trying to work out why this search doesn't work properly. I want to find all documents where instance=ko14274 but exclude any that are maxlevel=UNKNOWN. I have tried the following:



instance:ko14274 AND NOT maxlevel:UNKNOWN
instance:ko14274 AND -maxlevel:UNKNOWN
instance:ko14274 AND maxlevel:(-UNKNOWN)
instance:ko14274 AND -(maxlevel:UNKNOWN)




It still returns some results that should not be in the result set, but not all. is there a margin of error or estimation?


标签： javajava-8


解决方案









因此，就迭代次数而言，转换为 a 不太可能Map给您带来任何好处，您最好只浏览列表并就地处理。Foo这是必需的，因为在您浏览完整个s列表之前，无法知道您是否已到达特定部门 ID 的最后一次出现。



所以我会做类似的事情：



for (Foo foo : fooList) {
  if (hasBeenProcessed(foo.departmentId) {
    continue;
  }
  process(foo);
}




请注意，这hasBeenProcessed可能很简单，processedDepartmentIds.contains(foo.departmentId)具体取决于您的需要。



只是将其转换为地图，没有什么可以避免遍历整个列表。在Guava: Maps.toMap或Guava: Multimaps.index等库中有方便的方法。










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