# If. Then. Throw. Else. WTF?

Source: https://www.yegor256.com/2015/01/21/if-then-throw-else.html

This is the code I could never understand:

```java
if (x < 0) {
  throw new Exception("X can't be negative");
} else {
  System.out.println("X is positive or zero");
}
```

I have been trying to find a proper metaphor to explain its incorrectness.
Today I finally found it.


If-then-else is a [forking]({% pst 2016/aug/2016-08-10-if-then-else-code-smell %})
mechanism of procedural programming. The CPU
either goes to the left and **then** does something or goes to the right and
does something **else**. Imagine yourself driving a car and seeing this sign:

{% figure /images/2015/01/if-then-throw-1.png 500 %}

It looks logical, doesn't it? You can go in the left lane if you're not driving a truck.
Otherwise you should go in the right lane. Both lanes meet up
in a while. No matter which one you choose, you will end up on the same road.
This is what this code block does:

```java
if (x < 0) {
  System.out.println("X is negative");
} else {
  System.out.println("X is positive or zero");
}
```

Now, try to imagine this sign:

{% figure /images/2015/01/if-then-throw-2.png 500 %}

It looks very strange to me, and you will never see this sign anywhere
simply because a dead end means an *end*, a full stop, a finish.
What is the point of drawing a lane
after the dead end sign? There is no point.

This is how a proper sign would look:

{% figure /images/2015/01/if-then-throw-3.png 500 %}

This is how a proper code block would look:

```java
if (x < 0) {
  throw new Exception("X can't be negative");
}
System.out.println("X is positive or zero");
```

The same is true for loops. This is wrong:

```java
for (int x : numbers) {
  if (x < 0) {
    continue;
  } else {
    System.out.println("found positive number");
  }
}
```

While this is right:

```java
for (int x : numbers) {
  if (x < 0) {
    continue;
  }
  System.out.println("found positive number");
}
```

There is no road after the dead end! If you draw it, your code looks
like this very funny snippet I found a few years ago reviewing
sources written by some very well-paid developer in one very serious
company:

```java
if (x < 0) {
  throw new Exception("X is negative");
  System.exit(1);
}
```

Don't do this.