Which is more effective: if (null == variable) or if (variable == null)? [duplicate]

Question

In Java, which will be more effective, and what are the differences?

if (null == variable) 

or

if (variable == null) 

Answer 1

^{(Similar to this question: Difference between null==object and object==null)}

I would say that there is absolutely no difference in performance between those two expressions.

Interestingly enough however, the compiled bytecode (as emitted by OpenJDKs javac) looks a bit different for the two cases.

For boolean b = variable == null:

 3: aload_1               // load variable  4: ifnonnull 11          // check if it's null  7: iconst_1              // push 1  8: goto 12            11: iconst_0              // push 0 12: istore_2              // store 

For boolean b = null == variable:

 3: aconst_null           // push null  4: aload_1               // load variable  5: if_acmpne 12          // check if equal  8: iconst_1              // push 1  9: goto 13 12: iconst_0              // push 0 13: istore_2              // store 

As @Bozho says, variable == null is the most common, default and preferred style.

For certain situations however, I tend to put the null in front. For instance in the following case:

String line; while (null != (line = reader.readLine()))     process(line);