Java micro-benchmark on virtual method calls.

devirt.java

import com.google.caliper.SimpleBenchmark;

interface iface {
  int foo();
}

class base implements iface {
  public int foo() {
    return (int) System.nanoTime();
  }
}

final class sealed extends base {
}

final class sealedfinal extends base {
  public final int foo() {
    return super.foo();
  }
}

public final class devirt extends SimpleBenchmark {
  public static void main(String[] a) {
    int n = 0;
    final iface i = new base();
    n ^= i.foo();
    final base b = new base();
    n ^= b.foo();
    final sealed s = new sealed();
    n ^= s.foo();
    if (n == 0) {
      System.exit(42);
    }
  }

  public int timeInvokeInterfaceBase(final int n) {
    int d = 0;
    final iface o = new base();
    for (int i = 0; i < n; i++) {
      d ^= o.foo();
    }
    return d;
  }

  public int timeInvokeInterfaceFinal(final int n) {
    int d = 0;
    final iface o = new sealed();
    for (int i = 0; i < n; i++) {
      d ^= o.foo();
    }
    return d;
  }

  public int timeInvokeVirtualBase(final int n) {
    int d = 0;
    final base o = new base();
    for (int i = 0; i < n; i++) {
      d ^= o.foo();
    }
    return d;
  }

  public int timeInvokeVirtualFinal(final int n) {
    int d = 0;
    final base o = new sealed();
    for (int i = 0; i < n; i++) {
      d ^= o.foo();
    }
    return d;
  }

  public int timeInvokeFinal(final int n) {
    int d = 0;
    final sealed o = new sealed();
    for (int i = 0; i < n; i++) {
      d ^= o.foo();
    }
    return d;
  }

  public int timeInvokeFinalFinal(final int n) {
    int d = 0;
    final sealedfinal o = new sealedfinal();
    for (int i = 0; i < n; i++) {
      d ^= o.foo();
    }
    return d;
  }

}

Results on MacBook with Intel Core 2 Duo @ 2.66Ghz and Sun JVM 1.6.0_26:

 0% Scenario{vm=java, trial=0, benchmark=InvokeInterfaceBase} 60.39 ns; ?=2.75 ns @ 10 trials
17% Scenario{vm=java, trial=0, benchmark=InvokeInterfaceFinal} 60.75 ns; ?=2.35 ns @ 10 trials
33% Scenario{vm=java, trial=0, benchmark=InvokeVirtualBase} 60.73 ns; ?=2.44 ns @ 10 trials
50% Scenario{vm=java, trial=0, benchmark=InvokeVirtualFinal} 60.44 ns; ?=2.00 ns @ 10 trials
67% Scenario{vm=java, trial=0, benchmark=InvokeFinal} 60.79 ns; ?=2.18 ns @ 10 trials
83% Scenario{vm=java, trial=0, benchmark=InvokeFinalFinal} 60.67 ns; ?=1.84 ns @ 10 trials

           benchmark   ns linear runtime
 InvokeInterfaceBase 60.4 =============================
InvokeInterfaceFinal 60.8 =============================
   InvokeVirtualBase 60.7 =============================
  InvokeVirtualFinal 60.4 =============================
         InvokeFinal 60.8 ==============================
    InvokeFinalFinal 60.7 =============================

vm: java
trial: 0