Counter.java

// java.lang.VerifyError when returning an array of an interface

// Dalvik error message
// W/dalvikvm( 8228): VFY: returning [Ljava/lang/Object; (cl=0x0), declared [Ltest/Empty; (cl=0x40d5f510)
// W/dalvikvm( 8228): VFY:  rejecting opcode 0x11 at 0x000f
// W/dalvikvm( 8228): VFY:  rejected Ltest/Counter;.two_returns ()[Ltest/Empty;
// W/dalvikvm( 8228): Verifier rejected class Ltest/Counter;

// ART error message
// 7149  7149 E AndroidRuntime: java.lang.VerifyError: Verifier rejected class test.Counter: test.Empty[] test.Counter.two_returns() failed to verify: test.Empty[] test.Counter.two_returns(): [0xF] returning 'Reference: java.lang.Object[]', but expected from declaration 'Reference: test.Empty[]' (declaration of 'test.Counter' appears in /data/app/test-1/base.apk)

package test;

import android.app.Activity;
import android.os.Bundle;

interface Empty {
}

class A implements Empty {
}

class B implements Empty {
}

public class Counter extends Activity {

    // throws a VerifyError
    public Empty[] two_returns() {
      if (Math.random() > .5) {
        return new A[1];
      } else {
        return new B[1];
      }
    }

    // Does not throw a VerifyError
    public Empty[] one_return_A() {
      return new A[1];
    }

    // Does not throw a VerifyError
    public Empty[] one_return_B() {
      return new B[1];
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
      System.out.println(two_returns());
    }
}