java - 将新字符串添加到 hashmap java

Question

我正在编写一个程序来读取日志文件，然后计算某些字符串显示的次数。我试图手动输入字符串作为关键字，但由于有这么多，我决定搜索日志文件会更好，当它遇到“ua,”时，它应该创建一个新字符串，从“ua,”到该行的末尾，将其添加到 HashMap 中，并增加该特定字符串的计数(我感兴趣的所有字符串都以“ua,”开头)。我似乎无法弄清楚如何将新字符串添加到 HashMap 中。这是我到目前为止所拥有的。

public class Logs
{

public static void main(String args[]) throws IOException 
{

 Map<String, Integer> dayCount = new HashMap<String, Integer>();
    for (String str : KeyWords)
    {
        dayCount.put(str, 0);
    }

    File path = new File("C:\\P4logs"); 
    for(File f: path.listFiles())
    { // this loops through all the files + directories

        if(f.isFile()) 
        { // checks if it is a file, not a directory.

    try (BufferedReader br = new BufferedReader(new FileReader(f.getAbsolutePath())))
    {


String sCurrentLine;

while ((sCurrentLine = br.readLine()) != null) 
{
    boolean found = false;

    for (String str : DayCount.keySet()) 
    {
        if (sCurrentLine.indexOf(str) != -1)
        {
            DayCount.put(str, DayCount.get(str) + 1);
            found = true;
            break;
        }
     }
     if (!found && sCurrentLine.indexOf("ua, ") != -1)
     {
        System.out.println("Found an unknown user action: " + sCurrentLine);
        DayCount.put(key, value)    //not sure what to put here
     }
    }
   }
 for(String str : KeyWords)
    {
         System.out.println(str + " = " + DayCount.get(str));

    }

    }
   }
}

Answer 1

您无需遍历 HashMap 的键来查看是否存在!这违背了使用 HashMap 的目的(在您的解决方案中查找 O(1) 与 O(n) 没有冲突)。你应该只需要做这样的事情:

//If a key doesn't exist in a hashmap, `get(T)` returns null
if(DayCount.get(str) == null) {
    //We know this key doesn't exist, so let's create a new entry with 1 as the count
    DayCount.put(str, 1);
} else {
    //We know this key exists, so let's get the old count, increment it, and then update
    //the value
    int count = DayCount.get(str);
    DayCount.put(str, count + 1);
}

另一方面，请考虑遵循 Java 命名约定。变量应以小写字母开头(即 dayCount 与 DayCount)。只有类应该以大写字母开头。按照你现在的方式，看起来 DayCount 是一个类，它有一个名为 put 的静态方法。