CODEWITHSUNDEEP
javaperformance
webpersistence
webpersistence

Reputation: 904

Performance test for if statement branch

Is there any difference in performance between:

public int method()
{
    x = 1;
    if (x == 0)
       System.out.println("something");
    return 1;
}

And

public int method()
{
    x = 1;
    if (x == 0)
       System.out.println("something");
    else
       return 1;

    return 7; //this won't happen because x is 1
}

As you can notice I used an else in the second example. I do not know if the branching return is faster than the normal return.

Upvotes: 2

Views: 71

Answers (1)

user43968
user43968

Reputation: 2129

let's see the jvm instructions :

the first method one if branch: 

     public int ifmethod();
 0  aload_0 [this]
 1  iconst_1
 2  putfield ifperf.main.x : int [22]
 5  aload_0 [this]
 6  getfield ifperf.main.x : int [22]
 9  ifne 20
12  getstatic java.lang.System.out : java.io.PrintStream [24]
15  ldc <String "something"> [30]
17  invokevirtual java.io.PrintStream.println(java.lang.String) : void [32]
20  iconst_1
21  ireturn

the second method with else branch :

public int ifelsemethod();
 0  aload_0 [this]
 1  iconst_1
 2  putfield ifperf.main.x : int [22]
 5  aload_0 [this]
 6  getfield ifperf.main.x : int [22]
 9  ifne 23
12  getstatic java.lang.System.out : java.io.PrintStream [24]
15  ldc <String "something"> [30]
17  invokevirtual java.io.PrintStream.println(java.lang.String) : void [32]
20  goto 25
23  iconst_1
24  ireturn
25  bipush 7
27  ireturn

As you can see the both method are stricly identic in that case. the answer is at line 9 you have the test ifne ("IF Not Equal goto line XY") so in one case you go at line 20 and in the second at line 23. and then you execute the exact same instruction.

So in one case you will execute 0-9 -> 20,21 and in the other 0-9->23,24

Upvotes: 3

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