Ternary Operator - JAVA [duplicate]

Is it possible to change this:

if(String!= null) {

    callFunction(parameters);

} else {

    // Intentionally left blank

}

...to a ternary operator?

Solution 1:

Well, the ternary operator in Java acts like this...

return_value = (true-false condition) ? (if true expression) : (if false expression);

...Another way of looking at it...

return_value = (true-false condition) 
             ? (if true expression) 
             : (if false expression);

You question is kind of vague and we have to assume here.

If (and only if) callFunction(...) declares a non-void return value (Object, String, int, double, etc..) - it seems like it does not do that via your code - then you could do this...
```
return_value = (string != null) 
             ? (callFunction(...)) 
             : (null);
```
If callFunction(...) does not return a value, then you cannot use the ternary operator! Simple as that. You will be using something that you don't need.
- Please post more code to clear up any issues

Nonetheless, ternary operator should represent alternative assignments only!! Your code does not seem to do that, so you should not be doing that.

This is how they should work...

if (obj != null) {            // If-else statement

    retVal = obj.getValue();  // One alternative assignment for retVal

} else {

    retVal = "";              // Second alternative assignment for retVale

}

This can be converted to...

retVal = (obj != null)
       ? (obj.getValue())
       : ("");

Since it seems like you might be trying to just refactor this code to be a one-liner, I have added the following

Also, if your false-clause is truely empty, then you can do this...

if (string != null) {

    callFunction(...);

} // Take note that there is not false clause because it isn't needed

if (string != null) callFunction(...);  // One-liner

Solution 2:

Yes. You can with keeping same null in else block.

String result = str !=null ?  callFunction(parameters) : null;

Make sure that callFunction(parameters) return a String.

Solution 3:

The ternary operator can be used to combine two expressions but an empty statement is not an expression.

A method invocation can be used as an expression if the method returns a value (read: is not declared void) and it could be used together with a dummy constant null to form a ternary operator but the result would be again an expression which is not allowed in places where a statement is required, in other words, it can not replace an if statement.

By adding another construct taking an expression and imposing no additional side effect you can construct a complete replacement. E.g. by declaring and assigning a new, otherwise unused, local variable you get:

Object dummy=condition? callFunction(parameters): null;

But there is no benefit over simply saying if(condition) callFunction(parameters);. It might even add unnecessary overhead as it will perform auto-boxing if the return value is a primitive type.

With Java 8 there is a solution to the puzzle that works even for void methods:

((Runnable)(condition? ()->callFunction(parameters): ()->{})).run();

but it still has no advantage over simply using if.

Solution 4:

It could be possible if your method callFunction() has a return type. Then, you could do it like SURESH ATTA wrote in his answer:

String result = str!=null ? callFunction(str) : null;

Or with any other type for result or any other arguments. If you want to call a method in the else-Statement too, this one needs to have the same return type as the one in your if-statement.

If your method doesn't have a return type / the return type of callFunction() is void, it is not possible to change your if-else-statement into a ternary operator.