How to reset an array after each if statement?

I have this Java Program that I am writing where the user inputs 20 numbers and it gets stored in an array. Then you print an histogram that says how many times a number was inputted:

1-10 |*********

11-20 |*****

21-30 |**

31-40 |**

41-50 |**

This is my code:

 String asterisk1 = "";
String asterisk2 = "";
String asterisk3 = "";
String asterisk4 = "";
String asterisk5 = "";
System.out.println("Histogram: ");
System.out.println(" ");
for (int i = 0; i <= f.length-1; i++)
{
if (f[i] >= 1 && f[i] <= 10)
{
asterisk1 += "*";
}
if (f[i] >= 11 && f[i] <= 20)
{
asterisk2 += "*";
}
if (f[i] >= 21 && f[i] <= 30)
{
asterisk3 += "*";
}
if (f[i] >= 31 && f[i] <= 40)
{
asterisk4 += "*";
}
if (f[i] >= 41 && f[i] <= 50)
{
asterisk5 += "*";
}
}
System.out.println(" 1-10 |"+ asterisk1);
System.out.println("11-20 |"+ asterisk2);
System.out.println("21-30 |"+ asterisk3);
System.out.println("31-40 |"+ asterisk4);
System.out.println("41-50 |"+ asterisk5);
}
}

So instead of declaring every variable I tried creating an array. But the problem is I am confused how to reset the array to 0 so I get the correct amount of asterisks. I tried to just do String asterisk [] = new String[50]; and in the if loops I would just do asterisk[i] += "*"Any suggestions?

asterisk[i] += "*" here i is the index of your data means f's index but it should be the index of the range, specify directly like asterisk[0], asterisk[1]...

 if (f[i] >= 1 && f[i] <= 10) {
asterisk[0] += "*";
}
if (f[i] >= 11 && f[i] <= 20) {
asterisk[1] += "*";
}
...

Or you can use a nested loop for your condition dynamically

for (int i = 0; i <= f.length-1; i++) {
for(int j = 0; j < 5; j++) {
if (f[i] >= (j*10 +1) && f[i] <= (j+1)*10) {
asterisk[j] += "*";
}
}
}

I don't know what do you mean when you said

> how to reset the array to 0

But here I made a little example of what your program would like if you use a String array instead of five variables:

public class HelloWorld {
public static void main(String []args){
String[] asterisks = new String[5];  // set the size you want here
int[] f = { 0, 40, 52, 12, 31, 12, 42, 23, 5, 13, 42, 45, 25, 26, 27, };
// initialize every "space" of the array
for (int i=0; i<asterisks.length; i++) {
asterisks[i] = "";
}
// do exactly what your code did before, but with an Array
for (int i=0; i<f.length; i++) {
if (f[i] >= 1 && f[i] <= 10) {
asterisks[0] += "*";
} else if (f[i] >= 11 && f[i] <= 20) {
asterisks[1] += "*";
} else if (f[i] >= 21 && f[i] <= 30) {
asterisks[2] += "*";
} else if (f[i] >= 31 && f[i] <= 40) {
asterisks[3] += "*";
} else if (f[i] >= 41 && f[i] <= 50) {
asterisks[4] += "*";
}
}
System.out.println(" 1-10 |"+ asterisks[0]);
System.out.println("11-20 |"+ asterisks[1]);
System.out.println("21-30 |"+ asterisks[2]);
System.out.println("31-40 |"+ asterisks[3]);
System.out.println("41-50 |"+ asterisks[4]);
}
}

Maybe you would like to use a Hash to make it more dynamic, I mean: probably you will not know how many columns your histogram will have, so you could make a Hash that relate a range value ("21-30", "31-40", "41-50", etc...) to a position on the String Array. If you decide to follow my advice you couldn't do the last "System.out.println", you should for each the Hash keys first, and then println the String Array position correlated to every Hash key.

Sorry if I made mistakes writing this, English is not my native language.
I hope my example has been useful to you to understand how Arrays works.

Example of using Stream API:

• map each element of array to a certain range
• group the elements by their ranges and count the frequency of each element in the array
• build a histogram column containing appropriate number of asterisks

1. Define a function to generate a range 0_10, 11_20, etc. for the given integer value:

private static String buildRange(int x) {
    int ten = (x - 1) / 10 * 10; // correction to include multiple of 10 to "previous" range 
    return String.valueOf((x > 10 ? 1 : 0) + ten) + "_" + String.valueOf(10 + ten);
}

2. Convert the array into the frequency map.<br/>
   The map may be sorted by ranges in different ways: for this example it's ok to use TreeMap.

Arrays.stream(f)
      .boxed() // convert IntStream to Stream<Integer> to work with collectors
      .collect(Collectors.toMap( // build frequency map as Map<String, Integer>
              MyClass::buildRange, x -> 1, Integer::sum, TreeMap::new
      ))
      .entrySet().forEach(MyClass::printEntry);

3. Implement the method to print entry as a histogram column:

private static void printEntry(Map.Entry<String, Integer> entry) {
    System.out.printf("%5s | %s%n", 
            entry.getKey(), 
            String.join("", Collections.nCopies(entry.getValue(), "*")) 
            // or "*".repeat(entry.getValue()) for JDK 11+
    );
}

Output<br/>
For the input int[] f = { 0, 40, 52, 12, 31, 12, 42, 23, 5, 13, 42, 45, 25, 26, 27, };

 0_10 | **
11_20 | ***
21_30 | ****
31_40 | **
41_50 | ***
51_60 | *