Control flow as expressions

An expression is a statement that evaluates to a value. The following expression evaluates to true:

    "hello".startsWith("h")  

A statement, on the other hand, has no resulting value returned. The following is a statement because it assigns a value to a variable, but does not evaluate to anything itself:

    val a = 1 

In Java, the common control flow blocks, such as if...else and try..catch, are statements. They do not evaluate to a value, so it is common in Java, when using these, to assign the results to a variable initialized outside the block:

    public boolean isZero(int x) { 
      boolean isZero; 
      if (x == 0) 
        isZero = true; 
      else 
        isZero = false; 
      return isZero; 
    }

In Kotlin, the if...else and try..catch control flow blocks are expressions. This means the result can be directly assigned to a value, returned from a function, or passed as an argument to another function...