为什么Guava InputSupplier / OutputSupplier不扩展Supplier接口？

Question

My usecase is to be able to create a FileOutputStream without creating the file. So I have created this Guava based OutputStream:

public class LazyInitOutputStream extends OutputStream {

  private final Supplier<OutputStream> lazyInitOutputStreamSupplier;

  public LazyInitOutputStream(Supplier<OutputStream> outputStreamSupplier) {
    this.lazyInitOutputStreamSupplier = Suppliers.memoize(outputStreamSupplier);
  }

  @Override
  public void write(int b) throws IOException {
    lazyInitOutputStreamSupplier.get().write(b);
  }

  @Override
  public void write(byte b[]) throws IOException {
    lazyInitOutputStreamSupplier.get().write(b);
  }

  @Override
  public void write(byte b[], int off, int len) throws IOException {
    lazyInitOutputStreamSupplier.get().write(b,off,len);
  }


  public static LazyInitOutputStream lazyFileOutputStream(final File file) {
    return lazyFileOutputStream(file,false);
  }

  public static LazyInitOutputStream lazyFileOutputStream(final File file,final boolean append) {
    return new LazyInitOutputStream(new Supplier<OutputStream>() {
      @Override
      public OutputStream get() {
        try {
          return new FileOutputStream(file,append);
        } catch (FileNotFoundException e) {
          throw Throwables.propagate(e);
        }
      }
    });
  }

}

This works fine but I saw there were InputSupplier/OutputSupplier interfaces which I could have used... Except they do not extend Supplier so I can't use the memoization feature which is needed here because I don't want the OutputSupplier to behave like a factory.

In addition there is the Files api:

public static OutputSupplier<FileOutputStream> newOutputStreamSupplier(File file,
                                                       boolean append)

Is there a way I could use OutputSupplier and it would be more elegant than my current code?

Is there a reason why OutputSupplier doesn't implement Supplier?

Answer 1

InputSupplier可以引发IOException ，而Supplier不能。