What's the difference between -keep class com.sample.Foo {*;} and -keep class com.sample.Foo?

Question

I just built two release APKs.

One of them had

-keep class com.sample.Foo

And the other had

-keep class com.sample.Foo {*;}

When I decompiled the app on http://www.javadecompilers.com/apk , Foo was the same for both builds.

The code of Foo is below:

package com.sample;

import android.util.Log;

public class Foo {

    public int field;

    public Foo() {
        field = 90;
    }

    public int doSth() {
        doPrivate();
        return 2 * field;
    }

    private void doPrivate() {
        Log.d("Proguard", "doPrivate");
    }

    void doDef() {
        Log.d("Proguard", "doDef");
    }
}

That's how I made sure Foo and its methods weren't obfuscated:

package com.sample;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import java.lang.reflect.Method;


public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        try {
            Class<?> aClass = Class.forName("com.sample.Foo");
            Object instance = aClass.newInstance();
            Method method = aClass.getMethod("doSth");
            Integer res = (Integer) method.invoke(instance);
            Log.d("Proguard", "doSth res=" + res);
        } catch (Exception e) {
            Log.e("Proguard", "", e);
        }
    }
}

Update #1

My Proguard config.

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

Answer 1

The first one only keeps the class and its constructor.

The second one keeps the class and its constructor and any field or method inside the class.