Path: csiph.com!aioe.org!.POSTED!not-for-mail
From: Robert Spanjaard <spamtrap@arumes.com>
Newsgroups: comp.lang.java.programmer
Subject: Can't use block of statements as 'incrementer' in for loop?
Date: Wed, 14 Feb 2018 17:01:30 +0100
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Xref: csiph.com comp.lang.java.programmer:38020

When you create a for loop, you provide an initialisation statement, a 
condition, and a continue statement. Usually this continue statement is an 
incrementer or decrementer, but basically it can be any statement.

For instance, if you change Oracle's own tutorial example (*1)...

class ForDemo {
     public static void main(String[] args){
          for(int i=1; i<11; i++){
               System.out.println("Count is: " + i);
          }
     }
}

...with this...

class ForDemo {
     public static void main(String[] args){
          for(int i=1; i<11; System.out.println("haha")){
               System.out.println("Count is: " + i);
               i++;
          }
     }
}

... it still works.

Now, the same tutorial says "A block is a group of zero or more statements 
between balanced braces and can be used anywhere a single statement is 
allowed." (*2)

But when I replace the single haha-printing statement with any kind of 
block, the compiler produces an error message:

ForDemo.java:3: error: illegal start of expression
       for (int i=1; i<11; { i++; i++; }) {
                           ^

I must say I tried this construction purely out of curiosity, remembering 
Oracle's statement about blocks being allowed anywhere instead of a single 
statement, so I don't have a practical use case for it. But still I'd like 
to know why it doesn't work. So, can anyone of you shed some light on this 
issue? Google search doesn't really help in this case.

*1
https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html
*2
https://docs.oracle.com/javase/tutorial/java/nutsandbolts/expressions.html

-- 
Robert Spanjaard