文件拷贝

这个题目在笔试的时候经常出现，下面的代码给出了两种实现方案

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import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.nio.ByteBuffer; import java.nio.channels.FileChannel;   public final class MyUtil {       private MyUtil() {         throw new AssertionError();     }       public static void fileCopy(String source, String target) throws IOException {         try (InputStream in = new FileInputStream(source)) {             try (OutputStream out = new FileOutputStream(target)) {                 byte[] buffer = new byte[4096];                 int bytesToRead;                 while((bytesToRead = in.read(buffer)) != -1) {                     out.write(buffer, 0, bytesToRead);                 }             }         }     }       public static void fileCopyNIO(String source, String target) throws IOException {         try (FileInputStream in = new FileInputStream(source)) {             try (FileOutputStream out = new FileOutputStream(target)) {                 FileChannel inChannel = in.getChannel();                 FileChannel outChannel = out.getChannel();                 ByteBuffer buffer = ByteBuffer.allocate(4096);                 while(inChannel.read(buffer) != -1) {                     buffer.flip();                     outChannel.write(buffer);                     buffer.clear();                 }             }         }     } }

 注意：上面用到Java 7的TWR，使用TWR后可以不用在finally中释放外部资源 ，从而让代码更加优雅。