输出完毕后，需要close这个stream，从而使操作系统释放相关的资源。举例：
public void close( ) throws IOException
并不是所有的stream都需要close，可是，诸如file或者network，打开后，需要关闭。
try {
OutputStream out = new FileOutputStream("numbers.dat");
// Write to the stream...
out.close( );
}
catch (IOException ex) {
System.err.println(ex);
}
However, this code fragment has a potential leak. If an IOException is thrown while writing, the stream won't be closed. It's more reliable to close the stream in a finally block so that it's closed whether or not an exception is thrown. To do this you need to declare the OutputStream variable outside the try block. For example:
// Initialize this to null to keep the compiler from complaining
// about uninitialized variables
OutputStream out = null;
try {
out = new FileOutputStream("numbers.dat");
// Write to the stream...
}
catch (IOException ex) {
System.err.println(ex);
}
finally {
if (out != null) {
try {
out.close( );
}
catch (IOException ex) {
System.err.println(ex);
}
}
}