Java中用于简单文件（行数）功能的API

Java 8简短方法：

 Files.lines(Paths.get(fileName)).count();

但是大多数内存效率：

try(InputStream in = new BufferedInputStream(new FileInputStream(name))){    byte[] buf = new byte[4096 * 16];    int c;    int lineCount = 0;    while ((c = in.read(buf)) > 0) {       for (int i = 0; i < c; i++) {if (buf[i] == 'n') lineCount++;       }    }}

您根本不需要在此任务中使用String对象。