NIO利用磁盘映射 实现的文件内容查找

public class Grep {

// Charset and decoder for ISO-8859-15
private static Charset charset = Charset.forName("ISO-8859-15");
private static CharsetDecoder decoder = charset.newDecoder();

// Pattern used to parse lines
private static Pattern linePattern = Pattern.compile(".*\r?\n");

// The input pattern that we're looking for
private static Pattern pattern;

// Compile the pattern from the command line
private static void compile(String pat) {
try {
pattern = Pattern.compile(pat);
} catch (PatternSyntaxException x) {
System.err.println(x.getMessage());
System.exit(1);
}
}

// Use the linePattern to break the given CharBuffer into lines, applying
// the input pattern to each line to see if we have a match
//
private static void grep(File f, CharBuffer fileContent) {
Matcher lm = linePattern.matcher(fileContent); // Line matcher
Matcher pm = null; // Pattern matcher
int lines = 0;
while (lm.find()) {
lines++;
CharSequence cs = lm.group(); // The current line
if (pm == null)
pm = pattern.matcher(cs);
else
pm.reset(cs);
if (pm.find())
System.out.print(f + ":" + lines + ":" + cs);
if (lm.end() == fileContent.limit())
break;
}
}

// Search for occurrences of the input pattern in the given file
//
private static void grep(File f) throws IOException {

// Open the file and then get a channel from the stream
FileInputStream fis = new FileInputStream(f);
FileChannel fc = fis.getChannel();

// Get the file's size and then map it into memory
int sz = (int) fc.size();
MappedByteBuffer fileContent = fc.map(FileChannel.MapMode.READ_ONLY, 0, sz);

// Decode the file into a char buffer
CharBuffer cb = decoder.decode(fileContent);

// Perform the search
grep(f, cb);

// Close the channel and the stream
fc.close();
}

public static void main(String[] args) {
// if (args.length < 2) {
// System.err.println("Usage: java Grep pattern file...");
// return;
// }
String key = "a{2,3}";
compile(key);
// for (int i = 1; i < args.length; i++) {
File f = new File("C:\\test\\testCopyFile\\test1.txt");
try {
grep(f);
} catch (IOException x) {
System.err.println(f + ": " + x);
}
// }
}

}