Java ternary operator precedence ? Different outputs given

问题

I have the below code producing this output (no space after -1) ==> "1 3 -14 -15 -1"

int [] arr = {1, 3, Integer.MAX_VALUE, 4, Integer.MAX_VALUE, 5, Integer.MAX_VALUE};
for (int dist : arr) {
    System.out.print((dist == Integer.MAX_VALUE) ? -1 : dist + " ");
}

But if I evaluate the ternary expression separately (as shown below), it gives a different output (what I expected) ==> "1 3 -1 4 -1 5 -1"

int [] arr = {1, 3, Integer.MAX_VALUE, 4, Integer.MAX_VALUE, 5, Integer.MAX_VALUE}; 
for (int dist : arr) {
    int finalDist = (dist == Integer.MAX_VALUE) ? -1 : dist;
    System.out.print(finalDist + " ");          
}

What is going wrong with the first code snippet?

回答1:

Here

(dist == Integer.MAX_VALUE) ? -1 : dist + " "

The space will be added only if the condition is false. You should use parantheses to add " " at all times like below.

((dist == Integer.MAX_VALUE) ? -1 : dist) + " "

The ternary operator has only operator precedence over the assignment operators. (See below)

Oracle Site about Operator Precedence

The operators in the following table are listed according to precedence order. The closer to the top of the table an operator appears, the higher its precedence.

回答2:

It's just a simple problem with your parentheses. Try this:

int [] arr = {1, 3, Integer.MAX_VALUE, 4, Integer.MAX_VALUE, 5, Integer.MAX_VALUE};

    for (int dist : arr) {
        System.out.print(((dist == Integer.MAX_VALUE) ? -1 : dist) + " ");
    }

回答3:

You missed to put the operation within parenthesis, so it is behaving weirdly, use below code,

try{
        throw new ArithmeticException("Exception Testing...");
    }catch(Exception e){
        String msg = "First Statement : " + (e.getCause() != null ? e.getMessage() : null);

        System.out.println(msg);
     }

In case you need any other help or explanation on this . Please let me know.

来源：https://stackoverflow.com/questions/33857571/java-ternary-operator-precedence-different-outputs-given

标签

java

ternary-operator