a==null vs null==a

public class A{
        void a(){
                String a = null;
                if(a==null){}
        }
        void b(){
                String a = null;
                if(null==a){}
        }
}

void a();
  Code:
   Stack=1, Locals=2, Args_size=1
   0:   aconst_null
   1:   astore_1
   2:   aload_1
   3:   ifnonnull       6
   6:   return
  LineNumberTable: 
   line 3: 0
   line 4: 2
   line 5: 6

  StackMapTable: number_of_entries = 1
   frame_type = 252 /* append */
     offset_delta = 6
     locals = [ class java/lang/String ]


void b();
  Code:
   Stack=2, Locals=2, Args_size=1
   0:   aconst_null
   1:   astore_1
   2:   aconst_null
   3:   aload_1
   4:   if_acmpne       7
   7:   return
  LineNumberTable: 
   line 7: 0
   line 8: 2
   line 9: 7

  StackMapTable: number_of_entries = 1
   frame_type = 252 /* append */
     offset_delta = 7
     locals = [ class java/lang/String ]


}

今天看到一段代码，类似b方法的调用，于是就开始掉过来哪个快点。从BC上看a方法要快一点。具体的性能测试还有待验证。