Question

I have situation where my Java class needs to create a ton of certain kind of objects. I would like to give the name of the class of the objects that are created as a parameter. In addition, I need to give the created class a parameter in its constructor. I have something like

class Compressor {

    Class ccos;

    public Compressor(Class ccos) {
        this.ccos = ccos;
    }

    public int getCompressedSize(byte[] array) {
        OutputStream os = new ByteArrayOutputStream();
        // the following doesn't work because ccos would need os as its constructor's parameter
        OutputStream cos = (OutputStream) ccos.newInstance();
        // ..
    }
}

Do you have any ideas how I could remedy this?

Edit:

This is part of a research project where we need to evaluate the performance of multiple different compressors with multiple different inputs. Class ccos is a compressed OutputStream either from Java’s standard library, Apache Compress Commons or lzma-java.

Currently I have the following which appears to work fine. Other ideas are welcome.

OutputStream os = new ByteArrayOutputStream();
OutputStream compressedOut = (OutputStream) ccos.getConstructor(OutputStream.class).newInstance(os);
final InputStream sourceIn = new ByteArrayInputStream(array);

Answer 1

You can use the Class.getConstructor(paramsTypes...) method and call newInstance(..) on the constructor. In your case:

Compressor.class.getConstructor(Class.class).newInstance(Some.class);