3

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，我决定最好搜索日志文件，当它遇到“ua”时，它应该创建一个从“ua”到的新字符串在行尾，将其添加到哈希图中，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哈希图中。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));

    }

    }
   }
}

}

4

2 回答 2

7

您无需遍历 hashmap 的键来查看是否存在！这违背了使用哈希图的目的（O(1)没有冲突的查找与O(n)您的解决方案中的查找）。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dayCountvs DayCount）。只有类应该以大写字母开头。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，称为put.

于 2013-03-12T17:26:46.517 回答
0

由于这是您的要求 -

it should create a new string from "ua, " to the end of the line

由于不清楚一行是否以“ua”或“ua”开头，因此可能位于该行的中间。这大概就是它的样子——

  while ((sCurrentLine = br.readLine()) != null) 
    {

        if( sCurrentLine.indexOf("ua, ") != -1 ){
             String str = sCurrentLine.substr("ua, ");
             if(dayCount.get(str) != null){
                  dayCount.put(str, dayCount(str) +1 );
              }else{
                  dayCount.put(str, 1 ); 
              }
        }

    }
于 2013-03-12T17:40:16.630 回答