Why can't the left side of an assignment be an expression of an increment?

Question

Can someone tell me the value of “++” with an array in the following code in Java:

   int [ ] arr = new int[ 4 ];
   for(int i = 0; i < arr.length; i++){
        arr[ i ] = i + 1;
       System.out.println(arr[ i ]++);
   }

what does the arr[ i ]++meaning in the code above mean and why we cannot do:

arr[ i ]++ = i + 1;

Answer 1

The operator discussed here is called the postfix increment operator ( JLS 15.14.2 ). It is indicated that it behaves as follows:

• At run time, if the evaluation of the expression of the operand completes abruptly, then the expression of the incremental increment completes abruptly for the same reason and no increment occurs.
• 1 , .
  • (§5.6.2) 1 .
  • (. 5.1.3) / (§5.1.7) .
• postfix .

- : , arr[i]++ = v;, - , x++ = v;; postfix increment , .

JLS 15.1 , :

(), :

• [...] ( C lvalue)
• [...]
• ( )

, , x++ = v;.

JLS 15.26 :

. [...], , [...] . [...]

, :

int v = 42;
int x = 0;
x = v;        // OKAY!
x++ = v;      // illegal!
(x + 0) = v;  // illegal!
(x * 1) = v;  // illegal!
42 = v;       // illegal!
   // Error message: "The left-hand side of an assignment must be a variable"

, - , .

int[] arr = new int[3];
int i = 0;
arr[i++] = 2;
arr[i++] = 3;
arr[i++] = 5;
System.out.println(Arrays.toString(arr)); // prints "[2, 3, 5]"

Answer 2

System.out.println(arr[i]++) :

int tmp = arr[i];
arr[i] = arr[i] + 1;
System.out.println(tmp);

, ++ .

Answer 3

arr[i]++ " arr[i] 1" . arr[i] i+1 arr[ i ] = i + 1;. i + 2 arr[ i ]++ , , .. i + 1.

arr[ i ] = arr[i] + 1; , " arr[i] 1 ".

arr[ i ]++ = i + 1;, .

Answer 4

++ . (, , lvalue) 1. , ++ .

++ x, x ++. x, : ++ x x x ++ . , 1, 2, 3, 4 2, 3, 4, 5.

Answer 5

arr[ i ]++ arr [i] 1. :

arr[i] = i + 1;

As for arr[ i ]++ = i + 1;, do not try to write such code. Even if it compiles, it will be a puzzle for you or for others.

PS I would prefer:

++arr[i];

Answer 6

arr [i] ++ increments the value of arr [i] by one and assigns

as for arr[ i ]++ = i + 1;This phrase means something completely different, I do not know that it is even valid java to be honest. I would, if it worked, increase the value with arr [i], and then assign it to index + 1;