将新字符串添加到hashmap java

Question

我正在编写一个读取日志文件的程序,然后计算某些字符串的显示次数.我试图手动输入字符串作为关键字,但由于有这么多,我认为搜索日志文件会更好,当它遇到"ua"时,它应该创建一个从"ua"到该行的结尾,将其添加到hashmap,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.这就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

您不需要遍历hashmap的键来查看是否存在!这违背了使用散列图的目的(在解决方案中O(1)没有碰撞的查找O(n)).你应该只做这样的事情:

//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);
}

另请注意,请考虑遵循Java命名约定.变量应以小写字母开头(即dayCountvs DayCount).只有类应以大写字母开头.你现在拥有它的方式,它看起来像是DayCount一个带有静态方法的类put.