Swap String values without temporary variable

Question

I am aware of overflow, performance drops, etc but I need to swap two String values without any temporary variable. I know what cons are and found some effective methods but cannot understand one of them. ``` String a = "abc"; String b = "def"; b = a + (a = b).substring(0, 0); System.out.printf("A: %s, B: %s", a, b); ``` Output shows it clear values are swapped. When I look at this seems something related with priority operations but I cannot figure it out in my mind. Please, could someone explain to me what happens?

Accepted Answer

Basically you can think on the swap operation

```
b = a + (a = b).substring(0, 0);
```

as

```
b = "abc" + (a = "def").substring(0, 0);
```

In this first step I simply substituted the variables with their values (except from the `a` in the parenthesis, since this is assigning a value, and not reading).

Now `a` is equal to `"def"` and therefore `b` is:

```
b = "abc" + "def".substring(0, 0);
```

In this step I substituted the parenthesis with its value. And now that is clearly:

```
b = "abc";
```

since the method `.substring(0, 0)` returns an empty string.

So the swap is done.

Swap String values without temporary variable

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