The conditional operator, or ternary operator as it is otherwise known is a great way for assigning variables based on boolean tests. For example you may have seen the following : 

public class MonkeySniffer
{
    public static void main(String[] args)
    {

        int x = 5;
        String s;

        if (x < 10)
        {
            s = "Its less than 10";
        }
        else
        {
            s = "its greater than 10";
        }
        System.out.println(s);
    }
}

Pretty simple right? However that if-else statement is a bit messy considering all we’re doing is checking a condition and then using the output of that to assign a literal to our String reference.

A ternary operator allows us to perform the conditional check AND the assignment all in one line, it looks a bit like this in its psuedo code format

condition ? value if true : value if false

Lets modify the above sample to use the ternary operator. In plain English, we say that s is going to be assigned from either the true or the false condition based on the condition.

public class MonkeySniffer
{
    public static void main(String[] args)
    {

        int x = 5;
        String s;
        s = x < 10 ? "Its less than 10" : "its greater than 10";
        System.out.println(s);
    }
}

How much neater is that?! What happens is, the condition is evaluated, i.e., the “x < 10" part. If this equates to true then we assign s the first value, if its false, we assign s the second value.

That is pretty much all there is to it, lets have a look at some other examples, paste the following into your IDE and have a play.

public class MonkeySniffer
{
    public static void main(String[] args)
    {

        int x = 5;
        String s;
        s = x < 10 ? "Its less than 10" : "its greater than 10";
        System.out.println(s);

        s = x == 5 ? "x is 5" : "x is not 5";
        System.out.println(s);

        s = (x > 0 && x < 10) ? "bigger than zero, but less than 10" : "smaller than 0 or bigger than 10";
        System.out.println(s);
    }
}

Thats it, if you've got any comments please let me know!

Happy coding!

Further Reading :
Wikipedia conditional operator

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