LazyOutputStream.java

import java.io.IOException;
import java.io.OutputStream;

public class LazyOutputStream<T extends OutputStream> extends OutputStream {
    private final Factory<T> factory;
    private T stream;

    public LazyOutputStream(Factory<T> factory) {
        this.factory = factory;
    }

    public T get() throws IOException {
        return stream != null ? stream : (stream = factory.create());
    }

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

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

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

    @Override
    public void flush() throws IOException {
        get().flush();
    }

    @Override
    public void close() throws IOException {
        get().close();
    }

    public interface Factory<T extends OutputStream> {
        T create() throws IOException;
    }
}