在java中读取txt文件并将数据存储在哈希表中

我们需要确定的第一件事是你有一个 XY-Problem 因为“你需要做什么”和“你如何解决它”是完全不一致的。

那么让我们回到原来的问题,试着找出我们 需要 第一

尽我所能, source 和 action 连接,因为它们表示数据结构的可查询“键”,并且 probability , destination 和 reward 是数据结构中可查询的“结果”。因此,我们将首先创建对象来表示这两个概念:

public class SourceAction implements Comparable<SourceAction>{
    public final String source;
    public final String action;

    public SourceAction() {
        this("", "");
    }

    public SourceAction(String source, String action) {
        this.source = source;
        this.action = action;
    }

    public int compareTo(SourceAction sa) {
        int comp = source.compareTo(sa.source);
        if(comp != 0) return comp;
        return action.compareto(sa.action);
    }

    public boolean equals(SourceAction sa) {
        return source.equals(sa.source) && action.equals(sa.action);
    }

    public String toString() {
        return source + ',' + action;
    }
}

public class Outcome {
    public String probability; //You can use double if you've written code to parse the probability
    public String destination;
    public String reward; //you can use double if you're written code to parse the reward

    public Outcome() {
        this("", "", "");
    }

    public Outcome(String probability, String destination, String reward) {
        this.probability = probability;
        this.destination = destination;
        this.reward = reward;
    }

    public boolean equals(Outcome o) {
        return probability.equals(o.probability) && destination.equals(o.destination) && reward.equals(o.reward);

    public String toString() {
        return probability + ',' + destination + ',' + reward;
    }
}

那么,给定这些对象,如果 SourceAction 似乎有 一对多 与的关系 Outcome 物体?我的建议是 Map<SourceAction, List<Outcome>> 表示此关系。

private Map<SourceAction, List<Outcome>> readData() throws Exception {

可以使用哈希表(在这种情况下, HashMap )包含这些对象,但我试图使代码尽可能简单,因此我们将坚持使用更通用的接口。

然后,我们可以重用您在原始代码中使用的逻辑,将值插入到此数据结构中,只需进行一些调整。

private Map<SourceAction, List<Outcome>> readData() {
    //We're using a try-with-resources block to eliminate the later call to close the reader
    try (BufferedReader br = new BufferedReader (new FileReader("MyGridWorld.txt"))) {
        br.readLine();//Skip the first line because it's just a header

        //I'm using a TreeMap because that makes the implementation simpler. If you absolutely 
        //need to use a HashMap, then make sure you implement a hash() function for SourceAction
        Map<SourceAction, List<Outcome>> dataStructure = new TreeMap<>();

        //read file line by line
        String line = null;
        while ((line = br.readLine()) != null && !line.equals(";;")) {
            //split by tab
            String [] splited = line.split("\\t"); 
            SourceAction sourceAction = new SourceAction(splited[0], splited[1]);

            Outcome outcome = new Outcome(splited[2], splited[3], splited[4]);

            if(dataStructure.contains(sourceAction)) {
                //Entry already found; we're just going to add this outcome to the already
                //existing list.
                dataStructure.get(sourceAction).add(outcome);
            } else {
                List<Outcome> outcomes = new ArrayList<>();
                outcomes.add(outcome);
                dataStructure.put(sourceAction, outcomes);
            }
        }
    } catch (IOException e) {//Do whatever, or rethrow the exception}
    return dataStructure;
}

然后,如果要查询与给定源+操作关联的所有结果,只需构造 SourceAction源操作 对象并在地图中查询它。

Map<SourceAction, List<Outcome>> actionMap = readData();
List<Outcome> outcomes = actionMap.get(new SourceAction("(1,1)", "Up"));
assert(outcomes != null);
assert(outcomes.size() == 3);
assert(outcomes.get(0).equals(new Outcome("0.8", "(1,2)", "-0.04")));
assert(outcomes.get(1).equals(new Outcome("0.1", "(2,1)", "-0.04")));
assert(outcomes.get(2).equals(new Outcome("0.1", "(1,1)", "-0.04")));

这将产生您想要的功能 需要 解决你的问题。

您应该更改添加到哈希表的逻辑,以检查您创建的键。如果键存在,则获取它映射到的数组的数组列表,并将数组添加到其中。当前您将覆盖数据。

试试这个

if(hashTableForWorld.containsKey(key))
{
    value = hashTableForWorld.get(key);
    value.add(probDes);
    hashTableForWorld.put(key, value);
}
else
{
    value = new ArrayList<String[]>();
    value.add(probDes);
    hashTableForWorld.put(key, value);
}

然后,要打印内容,请尝试以下方法

for (Map.Entry<String, ArrayList<String[]>> entry : hashTableForWorld.entrySet()) {
    String key = entry.getKey();
    ArrayList<String[]> value = entry.getValue();

    System.out.println ("Key: " + key + " Value: ");
    for(int i = 0; i < value.size(); i++)
    {
        System.out.print("Array " + i + ": ");
        for(String val : value.get(i))
            System.out.print(val + " :: ")
        System.out.println();
    }
}

Hashtable 和 ArrayList (和其他集合)不复制键和值,因此存储的所有值都是相同的 probDes 刚开始分配的数组(请注意 String[] 以一种神秘的形式出现,你必须自己把它弄得漂亮,但你仍然可以看到它一直都是同一种神秘的东西)。
可以肯定的是,您应该分配一个新的 probDes公司 对于循环内的每个元素。
根据您的数据,您可以使用数组作为值在我看来,ArrayList没有真正的用途 这同样适用于 value ,遇到新的 key :

private Hashtable<String, ArrayList<String[]>> readData() throws Exception {
    try(BufferedReader br=new BufferedReader(new FileReader("MyGridWorld.txt"))) {
        br.readLine();

        Hashtable<String, ArrayList<String[]>> hashTableForWorld=new Hashtable<>();

        //read file line by line
        String line = null;
        while ((line = br.readLine()) != null && !line.equals(";;")) {
            //System.out.println("line ="+line);
            String source;
            String action;

            //split by tab
            String[] split = line.split("\\t"); 
            source = split[0];
            action = split[1];
            String key = source+","+action;

            String[] probDesRew = new String[3];
            probDesRew[0] = split[2];
            probDesRew[1] = split[3];
            probDesRew[2] = split[4];

            ArrayList<String[]> value = hashTableForWorld.get(key);
            if(value == null){
                value = new ArrayList<>();
                hashTableForWorld.put(key, value);
            }
            value.add(probDesRew);
        }
        return hashTableForWorld;
    }
}

除了将变量重新定位到其实际使用的位置之外,还将在本地创建返回值,并将读取器包装到一个try-with-resource构造中,该构造确保即使发生异常也会关闭它(请参见官方教程 here ).