How to create the FizzBuzz using loops in JAVA

问题

I'm writing this problem for school and I have some issues with it. I can't get "printFizzBuzz" to actually go up and calculate the wrapper function "FizzBuzz". I am required to use loops and was attempting to use a FOR loop. Beginner programmer here so no, I haven't used loops much at all. Any tips or pointers? ;)

The instructions are as follows.

public static String FizzBuzz(int number) 
{
    if( (number%3==0) && (number%5==0)) {
        return "FizzBuzz";
    }
    else if( number%3 == 0 ) {
        return "Fizz";
    } else if( number%5 == 0 ) {
        return "Buzz";
    } else {
        return ""+number;
    }
}

/*
 * use a for loop to print the appropriate FizzBuzz values (feel free to
 * call the provided FizzBuzz function) for values from from to to, 
 * including both of those values. Each value should be printed in a separate line.
 */
public static void printFizzBuzz(int from, int to, PrintStream out)
{
    for (int i = 1; i <= to; ++i){
        FizzBuzz(++i);
    }
}

回答1:

Take a look at the FizzBuzz function:

public static String FizzBuzz(int number)

public static STRING tells you that this function returns a string.

Each time you write
FizzBuzz(++i);
imagine this to be a string like "Fizz"

So in your program what you really wrote is

for (int i = 1; i <= to; ++i){
    "Fizz";
}

That doesn't look good right? You actually need to assign this string to something, or do some stuff with it. For example:

for (int i = 1; i <= to; ++i){
    String a = "Fizz";
    System.out.println(a);
}

Better, this is printing it to the standard output! However your function has already one PrintStream out parameter that you can use to print!

for (int i = 1; i <= to; ++i){
    String a = FizzBuzz(i++); 
    out.println(a);
}

Now let's take a look at the for loop: it creates a variable i that starts from 1 (int i = 1), checks the condition ( i <= to) and if the condition is satisfied it executes the body of the loop. After that it increments i by 1 (++i).

So the first 3 rounds of the loop will be unrolled like this:

    int i = 1;
    if(i<=to){
        String a = FizzBuzz(i++); 
        out.println(a);
    }
    ++i; //i = 3;
    if(i<=to){
        String a = FizzBuzz(i++); 
        out.println(a);
    }
    ++i; //i = 5;
    if(i<=to){
        String a = FizzBuzz(i++); 
        out.println(a);
    }
    ++i; //i = 7;

Looks like we still have a problem here. Why is i 3, then 5 and then 7? What happened to 2,4,6? The problem is that you are also incrementing i by 1 when calling FizzBuzz (FizzBuzz(i++)).

This is wrong, the loop is already incrementing i for you by 1, if you increment i by 1 more, it will be incremented by 2 each round.

I'll leave the final fix to you.

来源：https://stackoverflow.com/questions/39652324/how-to-create-the-fizzbuzz-using-loops-in-java

标签

java

loops

fizzbuzz