I don't understand the logic of code that is given below

Question

I have run this code in compiler and getting the output as 1 but I don't understand how it will be 1. Please explain with answer.

public class Main {
    public static void main(String args[]) {
        int a = 10;
        int b = 2;
        System.out.println((a < b) ? a++ : --b);
    }
}

Answer 1

The ternary operator ?: will check the condition (a < b) , since it is false, it will execute the expression after : , which is --b .

--b will subtract b by 1, and return the value after subtraction, which is 1.

Answer 2

The ternary operator is equivalent to a function that returns a value based on a condition. So let's write that function:

int ternary(int a, int b) {
  if(a < b) {
    int temp = a;
    temp = temp + 1;
    return a;
  } else {
    b = b - 1;
    return b;
  }
}

Answer 3

    int a = 10;
    int b = 2;
    System.out.println((a < b) ? a++ : --b);

In the above code (a < b) is checking if a is less than b and if its true a++ will be executed, and if it is false (which is the case in this situation) --b will be executed, and as the value of b is initialized as 2 it will equal to 1 after doing --b operation

because as per the turnery operator in java

Expression1 ? Expression2: Expression3;

If Expression1 is evaluated at true, Expression2 will be executed otherwise Expression3

Answer 4

There are several great answers already. This took a bit to edit for formatting, but hopefully useful to illustrate what's happening.

The interesting part of your program is in the println() statement:

System.out.println((a < b) ? a++ : --b)
                   ^^^^^^^^^^^^^^^^^^^

The whole thing inside the () is an expression with several things going on. At a high level, there is a boolean condition ( a < b ) followed by two other expressions: first is a++ , second is --b . Below is a breakdown.

(a < b) ? a++ : --b
 -----    ---   ---
   ^       ^     ^ 
   |       |     |__ second expression, used if condition is "false"
   |       |
   |       |__ first expression, used if condition is "true"
   |
   |__ this is the boolean condition to check; whatever is inside must return either true or false

This is how the entire expression is evaluated:

1. Is the boolean condtion true or false? To answer that, we need to know: what does a < b evaluate to? Since a = 10 , and b = 2 , we can substitute the values (10 for a, 2 for b). So the question becomes: what does 10 < 2 evaluate to? Since 10 is not less than 2, the result of the boolean condition is false .

2. Which of the of two expressions should we go to? Since the result from #1 was false , we skip the first expression ( a++ ), and go to the second one ( --b ).

3. What is --b ? That's a fancy way of saying: b = b - 1 and also use the new value of b as the result of the expression . Since b = 2 , it's equivalent to: b = 2 - 1 , and use the new b value ( 1 ) as the result of the expression. So this expression evaluates to "1", and that's what is printed out. This part is tricky though. A variation would be b-- instead of --b – if you did that , it would mean: set the new value of b to the result of "2 - 1" (so, new value is "1" like with --b ), but : for the expression result, use the old value . So --b ends up printing "1" in your example, and b-- would end up printing "2".