如何将布尔值true或false分配给字符串“ Open”和“ Close”

Question

So I have this code but I can't figure out the following:

1. Why does the output stop at 99? I know I set boolean[100] and I changed it to 101 but that didn't work.

2. How can I get the output to print "Locker x is open" or "Locker x is closed"? I know I have to somehow assign boolean true to open and false to closed.

Please help thanks!

Code

public class lockerPuzzle{

    public static void main(String[] args){
        boolean[] lockers = new boolean[100];
        for(int i = 1; i < lockers.length; i++){
            for (int j = i; j < lockers.length; j+=i){
                if (lockers[j] == false){
                    lockers[j] = true;
                }
                else{
                    lockers[j] = false;
                }
            }
        }

        for(int i = 1; i <lockers.length; i++){
            System.out.println(lockers[i] + " " + i);
        }
    }
}

Answer 1

Why does the output stop at 99?

You started at index 1, when you should have started at index 0.

Difference

1-99 (99 elements)

0-99 (100 elements)

Code

public static void main(String[] args){
    boolean[] lockers = new boolean[100];
    for(int i = 0; i < lockers.length; i++){
        for (int j = i; j < lockers.length; j+=i){
            if (lockers[j] == false){
                lockers[j] = true;
            }
            else{
                lockers[j] = false;
            }
        }
    }
    for(int i = 0; i <lockers.length; i++){
        System.out.println(lockers[i] + " " + i);
    }
}

How can I get the output to print Locker x is open or closed?

You can check the truth value of the boolean and print some text based on its value:

public class lockerPuzzle{

    public static void main(String[] args){

        // ...

        for(int i = 0; i < lockers.length; i++){
            boolean isOpened = lockers[i]

            if (isOpened) {
                System.out.println("Locker " + i + " is opened!");
            } else {
                System.out.println("Locker " + i + " is closed!");
            }
        }
    }
}

Note: This can be much more concise using more variables or ternary operators, but this will do for a new programmer. Good luck.

Answer 2

You are starting index from 1, Which will skip the first item in the Array. I have simplified your code here is the code, You don't really need those if statements

public static void main(String[] args){
    boolean[] lockers = new boolean[100];
    for(int i = 0; i < lockers.length; i++){
        for (int j = i; j < lockers.length; j+=i){
            lockers[j] = !lockers[j];
        }
    }
    for(int i = 1; i <lockers.length; i++){
        System.out.println(lockers[i] + " " + i);
    }
}