Ternary operator is not a statement

Question

I've the following ternary expression:

((!f.exists()) ? (f.createNewFile() ? printFile() : throw new Exception("Error in creating file")) : printFile());

For one, or more, reason that I don't know idea IDE say to me that it isn't a statement. Why?

Answer 1

this is not valid, you need to return a value

printFile() : throw new Exception("Error in creating file")

try this one

if(f.exists() || f.createNewFile()) {
  printFile();
}else{
  throw new Exception("Error in creating file");
}

Answer 2

It looks like you are using it as a statement and not as an assignment

From what SO says it is not possible to do so

Also from another SO Articel, that says you can´t throw an exception in the ternary statement

I think you need to go back to an if-else clause like this:

if (!f.exists()) {
   try {
      f.createNewFile();
      printFile();
   } catch(Exception e ) {
      System.out.println("Error in creating file");
   }
} else {
   printFile();
}

Answer 3

The "COND ? Statement : Statement" construct is an expression. It can not be used as a statement. Without assignment it can be used in situation like resolving condition argument in function call or string concatenation.

Func( (COND ? param1 : param2) );
"Hi"+(con?"Miss":"Mr.")+"";

Answer 4

The statements in the ternary operator need to be non-void . They need to return something.

Example:

• Consider a case, where count variable gets incremented and I am checking for its value and return true or false above certain threshold.
• System.out.println((count >10 ? true: false));
• As compared to, count >10 ? true: false count >10 ? true: false where compiler will complain that this is not a statement.