java - 获取HashMap值的count个数

Question

使用此 link 中的代码将文本文件内容加载到 GUI:

Map<String, String> sections = new HashMap<>();
Map<String, String> sections2 = new HashMap<>();
String s = "", lastKey="";
try (BufferedReader br = new BufferedReader(new FileReader("input.txt"))) {
    while ((s = br.readLine()) != null) {
        String k = s.substring(0, 10).trim();
        String v = s.substring(10, s.length() - 50).trim();
        if (k.equals(""))
            k = lastKey;
        if(sections.containsKey(k))
            v = sections.get(k) + v; 
        sections.put(k,v);
        lastKey = k;
    }
} catch (IOException e) {
}
System.out.println(sections.get("AUTHOR"));
System.out.println(sections2.get("TITLE"));

如果 input.txt 的内容为:

AUTHOR    authors name
          authors name
          authors name
          authors name
TITLE     Sound, mobility and landscapes of exhibition: radio-guided
          tours at the Science Museum

现在我想计算 HashMap 中的值，但是 sections.size() 计算存储在文本文件中的所有数据行。

我想问一下如何计算项目，即sections中的值v？如何根据作者姓名获得编号4？

Answer 1

由于作者具有一对多关系，因此您应该将其映射到 List 结构而不是 String。

例如:

Map<String, ArrayList<String>> sections = new HashMap<>();
Map<String, String> sections2 = new HashMap<>();
String s = "", lastKey="";
try (BufferedReader br = new BufferedReader(new FileReader("input.txt"))) {
    while ((s = br.readLine()) != null) {
        String k = s.substring(0, 10).trim();
        String v = s.substring(10, s.length() - 50).trim();
        if (k.equals(""))
            k = lastKey;

        ArrayList<String> authors = null;
        if(sections.containsKey(k))
        {
            authors = sections.get(k);
        }
        else
        {
            authors = new ArrayList<String>();
            sections.put(k, authors);
        }
        authors.add(v);
        lastKey = k;
    }
} catch (IOException e) {
}

// to get the number of authors
int numOfAuthors = sections.get("AUTHOR").size();

// convert the list to a string to load it in a GUI
String authors = "";
for (String a : sections.get("AUTHOR"))
{
    authors += a;
}