如何创建使用循环格式化数组输出的方法

Question

I am creating a class that calls methods on an array of unknown size and unknown values. I have the entire thing made except the method that formats the output. The class is about locker rentals. If the first locker has been rented for two days, then this would be true:

    daysLeftRental[0] == 2;

If the locker is available to rent, then this would be true:

    daysLeftRental[0] == -1;

In other words, any lockers that are available hold a value of -1, since there is no way someone could rent a locker for -1 days. I need to format my output in the following manner:

    Locker 0: 3
    Locker 1: Available
    Locker 2: 30

And so on and so forth. I have no idea how I would format my code so that when

    i = position of locker;
    daysLeftRental[i] == -1;

my output says "Available" and when

    daysLeftRental[i] >= 0

my output says whatever value is stored in daysLeftRental[i]. For reference, this is what my code would look like if I could just return -1 instead of the string "available"

    public String toString() {
        String formatOutput = " ";
        for (int i = 0; i < daysLeftRental.length; i++) {
             formatOutput = formatOutput + "\nLocker" 
             + i + ": " + daysLeftRental[i];
        }
        return formatOutput;
    }

which would yield:

    Locker 0: 3
    Locker 1: -1
    Locker 2: 30

Answer 1

Is this the one you are trying?

public String toString() {
        String formatOutput = " ";
        for (int i = 0; i < daysLeftRental.length; i++) {
             formatOutput = formatOutput + "\nLocker " 
             + i + ": " + (daysLeftRental[i] == -1 ? "Available" : daysLeftRental[i].toString());
        }
        return formatOutput;
    }

Answer 2

you can do it like this:

public String toString() {
    String formatOutput = " ";
    for (int i = 0; i < daysLeftRental.length; i++) {
         if(daysLeftRental[i] >= 0){
             formatOutput = formatOutput + "\nLocker" 
             + i + ": " + daysLeftRental[i];
         }else{
             formatOutput = formatOutput + "\nLocker" 
             + i + ": Available";        
         }
    }
    return formatOutput;
}

or, you can prepare the line before the if-statement, then just append last segmant:

public String toString() {
    String formatOutput = " ";
    for (int i = 0; i < daysLeftRental.length; i++) {
         formatOutput = formatOutput + "\nLocker" + i + ": ";
         if(daysLeftRental[i] >= 0){
              formatOutput += Integer.toString(daysLeftRental[i]);
         }else{
             formatOutput += "Available";        
         }
    }
    return formatOutput;
}

if you don't like to write same line in both if and else, you can use a variable to hold the number or the word "Available"

public String toString() {
    String formatOutput = " ";
    String status = "";

    for (int i = 0; i < daysLeftRental.length; i++) {
         if(daysLeftRental[i] >= 0){
             status = Integer.toString(daysLeftRental[i]);
         }else{
             status = "Available";
         }

         //concatenate it:
         formatOutput = formatOutput + "\nLocker" + i + status;
    }
    return formatOutput;
}

and you can use inline-if as in Aruna's answer above (if you understand it) if not, i would recommend (option-2) , no much code repeated (option-1), no much variables declared (option-3).

EDIT: - -- -- -- --

i don't want to exaggerate, but you can always use a method, if you know how to use them create a method that will return either the number or "Available"., the IF-statement goes to the method, and that's it

public String getStatus(int x){

    if(x>=0){
        return Integer.toString(x);
    }else{
        return "Available";
    }
}

in the for loop, don't use IF-statement at all. just concatenate the result of getStatus() call to the line

formatOutput = formatOutput + "\nLocker" + i + ": " + getStatus(daysLeftRental[i]);