我不懂一行简单的代码

Question

Below is line:

if (!seatNum[i]) 

I don't understand the purpose of this line.Code:

 if(economyClass<5) {
    for(int i=5;i<seatNum.length;i++) {
        if(!seatNum[i]) {
            seatNum[i]=true;
            System.out.println("Economy Class. Seat number: "+(i+1));
            economyClass++;
            break;
        }
    }
 }

Answer 1

It looks like seatNum is array of boolean, which mark if seat is taken.

if(!seatNum[i]) is if seat not taken, similar but shorter way of checking seatNum[i] == false

You are marking it as taken seatNum[i]=true; and increase the economyClass number by economyClass++;

Answer 2

Supposing that seatNum[] is an array of booleans , that means: if the element at index i of seatNum is false, then proceed.

you can also read that as : if(seatNum[i] == false)

Answer 3

seatNum[] must be a boolean array and !seatNum[i] expands to (seatNum[i]==false) which evaluates to true or false . So it is checking if seatNumber is not occupied and if not occupied alloting it.

Answer 4

In Java, the ! is also called Boolean negation operator and what it does is inverting a boolean value:

!true => false
!false => true

In order for the posted code to compile the seatNum array should contain booleans.

Answer 5

I can assume seatNum array as of boolean type as you have not mentioned the data type of array seatNum. And if I am correct in my assumption, the content of array in the ith index can be true or false, if !true which is equals to false, the immediate line of the code sets true in the ith index. In one line, ! is a logical not operator and not of true means false.

Hope this helps you to explore more about operators in java