Is there any computational difference between while and for loops?

Question

Just wondering if there is any computational difference between:

for(;condition;) {
    //task
}

and

while(condition) {
    //task
}

In both structures the Condition is tested one more time then the execution of body, so there is no computational difference. — Adnan Ahmad Khan
– Adnan Ahmad Khan, Commented Mar 12, 2019 at 7:22
Try compiling both of these, and looking at the byte code. Let us all know if you see any difference at all. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Mar 12, 2019 at 7:22
The only practical difference between that kind of for-loop, and a while-loop, is if you use continue. — hyde
– hyde, Commented Mar 12, 2019 at 8:05

Amit Bera · Accepted Answer · 2019-03-12 08:02:33Z

10

There is no difference as in both the cases Java compiler generates the same byte code . If you look on the byte code when I used for loop:

  0: bipush        11
  2: istore_1
  3: goto          9
  6: iinc          1, -1
  9: iload_1
 10: bipush        10
 12: if_icmpgt     6
 15: return

The above byte code genearated for the code below :

    int a = 11;
    for (; a > 10;) {
        a--;
    }

And same byte code:

   Code:
      0: bipush        11
      2: istore_1
      3: goto          9
      6: iinc          1, -1
      9: iload_1
     10: bipush        10
     12: if_icmpgt     6
     15: return

Has generated by the compiler when I used while loop

    int a = 11;
    while (a > 10) {
        a--;
    }

edited Mar 12, 2019 at 8:02

answered Mar 12, 2019 at 7:29

Amit Bera

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Comments

gbandres · Accepted Answer · 2019-03-12 07:23:07Z

1

The only difference between for and while is the syntax. Java will compile them to the exactly same code so there's no computational difference. Here is an article in the matter.

answered Mar 12, 2019 at 7:23

gbandres

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2 Comments

M. Deinum Over a year ago

Not sure if that article is the best one, next to that it doesn't really show if it compiles to exactly the same code. It shows only a sketchy benchmark.

gbandres Over a year ago

You are right, Admin Bera's answer is a better proof.

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