Java NIO FileChannel读

墨蓝 2023-10-18 15:13 88阅读 0赞

import java.io.BufferedReader;
    import java.io.FileInputStream;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.io.RandomAccessFile;
    import java.nio.ByteBuffer;
    import java.nio.channels.FileChannel;
    
    public class FileTest {
    	public static void main(String[] args) {
    		try {
    			new FileTest();
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    
    	public FileTest() throws Exception {
    		String path = "D:/code/file.txt";
    		RandomAccessFile raf = new RandomAccessFile(path, "rw");
    		FileChannel fc = raf.getChannel();
    		System.out.println("文件总长度:" + fc.size());
    
    		System.out.println("文件全部内容:");
    		printer(path);
    
    		final int capacity = 3;
    		ByteBuffer buffer = ByteBuffer.allocate(capacity);
    
    		int count = 0;
    		while (true) {
    			System.out.println("=============");
    			System.out.println("从此位置开始读:" + fc.position());
    
    			buffer.clear();
    
    			count = fc.read(buffer);
    			if (count == -1) {
    				break;
    			}
    
    			System.out.println("读取的数据:" + new String(buffer.array(), 0, count));
    		}
    	}
    
    	// 打印path指向的文件中的内容。
    	private void printer(String path) throws Exception {
    		InputStream is = new FileInputStream(path);
    		BufferedReader br = new BufferedReader(new InputStreamReader(is));
    		String s = null;
    		while (true) {
    			s = br.readLine();
    			if (s != null)
    				System.out.println(s);
    			else
    				break;
    		}
    
    		br.close();
    		is.close();
    	}
    }

程序运行输出：

文件总长度:10
    文件全部内容:
    0123456789
    =============
    从此位置开始读:0
    读取的数据:012
    =============
    从此位置开始读:3
    读取的数据:345
    =============
    从此位置开始读:6
    读取的数据:678
    =============
    从此位置开始读:9
    读取的数据:9
    =============
    从此位置开始读:10