Question

我有一个文本文件，我试图从中搜索具有多行的字符串。我可以搜索一个字符串，但是我需要搜索多行字符串。

我已尝试搜索运行正常的单行。

public static void main(String[] args) throws IOException 
{
  File f1=new File("D:\\Test\\test.txt"); 
  String[] words=null;  
  FileReader fr = new FileReader(f1);  
  BufferedReader br = new BufferedReader(fr); 
  String s;     
  String input="line one"; 

  // here i want to search for multilines as single string like 
  //   String input ="line one"+
  //                 "line two";

  int count=0;   
  while((s=br.readLine())!=null)   
  {
    words=s.split("\n");  
    for (String word : words) 
    {
      if (word.equals(input))   
      {
        count++;    
      }
    }
  }

  if(count!=0) 
  {
    System.out.println("The given String "+input+ " is present for "+count+ " times ");
  }
  else
  {
    System.out.println("The given word is not present in the file");
  }
  fr.close();
}

以下是文件内容。

line one  
line two  
line three  
line four

Answer 1

为此使用StringBuilder，从文件中读取每一行，并使用StringBuilder将它们附加到lineSeparator

StringBuilder lineInFile = new StringBuilder();

while((s=br.readLine()) != null){
  lineInFile.append(s).append(System.lineSeparator());
}

现在使用searchString检查lineInFile中的contains

StringBuilder searchString = new StringBuilder();

builder1.append("line one");
builder1.append(System.lineSeparator());
builder1.append("line two");

System.out.println(lineInFile.toString().contains(searchString));

Answer 2

尝试一下

public static void main(String[] args) throws IOException {
    File f1 = new File("./src/test/test.txt");
    FileReader fr = new FileReader(f1);
    BufferedReader br = new BufferedReader(fr);
    String input = "line one";
    int count = 0;

    String line;
    while ((line = br.readLine()) != null) {
        if (line.contains(input)) {
            count++;
        }
    }

    if (count != 0) {
        System.out.println("The given String " + input + " is present for " + count + " times ");
    } else {
        System.out.println("The given word is not present in the file");
    }
    fr.close();
}

Answer 3

为什么不只将文件中的所有行标准化为一个字符串变量，然后仅计算文件中输入出现的次数。我已经使用Regex来计算发生次数，但是可以按照您认为合适的任何自定义方式进行。

public static void main(String[] args) throws IOException 
{
        File f1=new File("test.txt"); 
        String[] words=null;  
        FileReader fr = new FileReader(f1);  
        BufferedReader br = new BufferedReader(fr); 
        String s;     
        String input="line one line two"; 

        // here i want to search for multilines as single string like 
        //   String input ="line one"+
        //                 "line two";

        int count=0;
        String fileStr = "";
        while((s=br.readLine())!=null)   
        {
            // Normalizing the whole file to be stored in one single variable
            fileStr += s + " ";
        }

        // Now count the occurences
        Pattern p = Pattern.compile(input);
        Matcher m = p.matcher(fileStr);
        while (m.find()) {
            count++;
        }

        System.out.println(count); 

        fr.close();
}

使用StringBuilder类进行有效的字符串连接。

Answer 4

默认C语言提供的更复杂的解决方案（代码基于《 The C编程语言》书中的代码）

final String searchFor = "Ich reiß der Puppe den Kopf ab\n" +
        "Ja, ich reiß' ich der Puppe den Kopf ab";

int found = 0;

try {
    String fileContent = new String(Files.readAllBytes(
        new File("puppe-text").toPath()
    ));

    int i, j, k;
    for (i = 0; i < fileContent.length(); i++) {
        for (k = i, j = 0; (fileContent.charAt(k++) == searchFor.charAt(j++)) && (j < searchFor.length());) {
            // nothig
        }

        if (j == searchFor.length()) {
            ++found;
        }
    }
} catch (IOException ignore) {}

System.out.println(found);

Answer 5

尝试使用Scanner.findWithinHorizon（）

String pathToFile = "/home/user/lines.txt";
String s1 = "line two";
String s2 = "line three";

String pattern = String.join(System.lineSeparator(), s1, s2);

int count = 0;
try (Scanner scanner = new Scanner(new FileInputStream(pathToFile))) {
  while (scanner.hasNext()) {
    String withinHorizon = scanner.findWithinHorizon(pattern, pattern.length());
    if (withinHorizon != null) {
      count++;
    } else {
      scanner.nextLine();
    }

  }
} catch (FileNotFoundException e) {
  e.printStackTrace();
}
System.out.println(count);

在文本文件中搜索多行字符串

5 个答案: