java9版本特性资源自动关闭的语法增强

@Test
void testStream() throws IOException {
  String fileName = "D:\\data\\test\\testStream.txt";
  FileOutputStream fos = new FileOutputStream(fileName);  //创建IO管道流
  OutputStreamWriter osw = new OutputStreamWriter(fos);
  BufferedWriter bw = new BufferedWriter(osw);
  try{
    bw.write("手写代码进行Stream流的关闭");
    bw.flush();
  }finally{
    bw.close();   //手动关闭IO管道流
    osw.close();
    fos.close();
  }
}

@Test
void testTry() throws IOException {
  String fileName = "D:\\data\\test\\testTry.txt";
  try(FileOutputStream fos = new FileOutputStream(fileName);
      OutputStreamWriter osw = new OutputStreamWriter(fos);
      BufferedWriter bw = new BufferedWriter(osw);){
    bw.write("IO管道流被自动调用close()方法");
    bw.flush();
  }
}

public interface Closeable extends AutoCloseable {
    public void close() throws IOException;
}

@Test
void testJava9Try() throws IOException {
  String fileName = "D:\\data\\test\\testJava9Try.txt";
  FileOutputStream fos = new FileOutputStream(fileName);
  OutputStreamWriter osw = new OutputStreamWriter(fos);
  BufferedWriter bw = new BufferedWriter(osw);
  try(bw;osw;fos){  //注意这里：尝试去回收这三个对象对应的资源，和上文中的java 7代码对比
    bw.write("Java9-可以被自动调用close()方法");
    bw.flush();
  }
}