Java 中的 HashMap 单值检索

Question

我创建了下面列出的 HashMap：

Map<String, List<Double>> hm1 = new HashMap<String, List<Double>>();    
List<Double> hmValues1 = new ArrayList<Double>();

并使用下面的方法从文件中添加值，其中文件的指定值是：

line1 0.418 0.24968 -0.41242 0.1217 0.34527 -0.044457 -0.49688 -0.17862 0.00066023 -0.6566 
line2 0.013441 0.23682 -0.16899 0.40951 0.63812 0.47709 -0.42852 -0.55641 -0.364 -0.23938
line3 -0.418 -0.24968 0.41242 -0.1217 -0.34527 -0.16899 -0.40951 -0.63812 -0.47709 0.42852

我能够打印键的所有值：line1，但我想检索列表的各个值，以单独处理它们。

public static void conceptHashMap() {
    int len,i=0;
    double dVal=0.0;
    String strLine;
    String conceptSearch = "line1";     // will be a key in hashmap

    try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {

        while ((strLine = br.readLine()) != null) {
            String[] dims = strLine.split(" ");
            len = dims.length;
            if (dims[i++].equals(conceptSearch)) {
                while (--len>0) {
                    dVal=Double.parseDouble(dims[i++]);
                    hmValues1.add(dVal);
                }
                hm1.put(conceptSearch, hmValues1); 
                for (Map.Entry<String, List<Double>> entry : hm1.entrySet()) {
                    String key = entry.getKey();
                    List<Double> hmvalues1 = entry.getValue();
                    System.out.println("key value pair");
                    System.out.println("Key = " + key);
                    System.out.println("Values = " + hmvalues1);
                }
                break;  
            }
            i=0; 
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Answer 1

public static void conceptHashMap() {
int len,i=0;
double dVal=0.0;
String strLine;
String conceptSearch = "line1";     // will be a key in hashmap

try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {

    while ((strLine = br.readLine()) != null) {
        String[] dims = strLine.split(" ");
        len=dims.length;
        if(dims[i++].equals(conceptSearch)){
            while(--len>0) {
                dVal=Double.parseDouble(dims[i++]);
                hmValues1.add(dVal);
            }
            hm1.put(conceptSearch, hmValues1); 
            for (Map.Entry<String, List<Double>> entry : hm1.entrySet()) {
                String key = entry.getKey();
                List<Double> hmvalues1 = entry.getValue();
                System.out.println("key value pair");
                System.out.println("Key = " + key);
                System.out.println("Values = " + hmvalues1);
                // simply iterate the list to get each single value 
                for(Double hmvalue : hmvalues1){
                      System.out.println(hmvalue);
                }

            }
            break;  
        }
        i=0; 
    }
} catch (IOException e) {
    e.printStackTrace();
    }
}

您可以简单地获取列表中的每个值并执行您需要的任何操作。

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