跳轉到.txt文件中的特定行，其中所有行的長度都等於Java

Question

我有一個包含大約100萬行信息的文本文件。鑑於我知道我想要哪條線，並且所有線條的長度相等，我正在尋找一種方法來跳轉到特定線條。

我讀過，有可能這樣做，而不必每行都讀一行，因爲所有行都相等。如果是這樣，任何人都可以提供一個示例代碼，我該如何做到這一點？或者，我最好簡單地閱讀每一行並循環播放它？

Answer 1

您正在尋找這樣的：

String line = FileUtils.readLines(file).get(lineNumber); 

，或者你可以嘗試使用迭代器，像這樣： -

LineIterator l= IOUtils.lineIterator(new BufferedReader(new FileReader("file.txt"))); 
for (int lineNumber = 0; l.hasNext(); lineNumber++) { 
    String line = (String) l.next(); 
    if (lineNumber == desiredLineNumber) { 
     return line; 
    } 
} 

編輯： -

從here： -

int sizeofrecordinbytes = 290; 
// for this example this is 1 based, not zero based 
int recordIWantToStartAt = 12400; 
int totalRecordsIWant = 1000; 

File myfile = new File("someGiantFile.txt"); 


// where to seek to 
long seekToByte = (recordIWantToStartAt == 1 ? 0 : ((recordIWantToStartAt-1) * sizeofrecordinbytes)); 

// byte the reader will jump to once we know where to go 
long startAtByte = 0; 

// seek to that position using a RandomAccessFile 
try { 
     // NOTE since we are using fixed length records, you could actually skip this 
     // and just use our seekToByte as the value for the BufferedReader.skip() call below 

    RandomAccessFile rand = new RandomAccessFile(myfile,"r"); 
    rand.seek(seekToByte); 
    startAtByte = rand.getFilePointer(); 
    rand.close(); 

} catch(IOException e) { 
    // do something 
} 

// Do it using the BufferedReader 
BufferedReader reader = null; 
try { 
    // lets fire up a buffered reader and skip right to that spot. 
    reader = new BufferedReader(new FileReader(myfile)); 
    reader.skip(startAtByte); 

    String line; 
    long totalRead = 0; 
    char[] buffer = new char[sizeofrecordinbytes]; 
    while(totalRead < totalRecordsIWant && (-1 != reader.read(buffer, 0, sizeofrecordinbytes))) { 
     System.out.println(new String(buffer)); 
     totalRead++; 
    } 
} catch(Exception e) { 
    // handle this 

} finally { 
    if (reader != null) { 
     try {reader.close();} catch(Exception ignore) {} 
    } 
} 

Answer 2

I gue SS你正在尋找一個隨機文件訪問

File file = ...; 
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r"); 
int lineNumber = ...; // first line number is 0 
int lineWidth = ...; // your fixed line width 
long beginIndexOfLine = lineWidth * lineNumber; 
randomAccessFile.seek(beginIndexOfLine); 

byte[] line = new byte[lineWidth]; 
randomAccessFile.read(line);