I need help designing a method that finds the percentile of a value given the percentile rank. Here are the exact instructions:

public double getPercentile(int p)
This returns the value of the pth percentile. A value stored in the array is the pth percentile if it is greater than or equal to at least p% of the values and less than or equal to at least (100-p)% of the values. Return the first value in the array that satisfies these conditions. if p is not between 0 and 100 (inclusive), return 0. If the array is empty, return 0. Otherwise, there should be at least one value in the array satisfying the condition.
Hint: Write a private helper method that determines whether a given value is the pth percentile. Call this for each element in the array until you find one that works.

I figured out how to do getRank() on my own but I'm having trouble figuring out how to do it the other way around basically.

``````package pr02;

public class Percentile {
private int size;
private double capacity;
private double[] array;

public Percentile(double cap) {
size = 0;
capacity = cap;
array = new double[(int) capacity];

}

if (size < capacity) {
array[size] = value;
size++;
return true;
} else
return false;
}

public int getRank(double value){
double scoresLessThan = 0;
double rank = 0;
for (int i=0; i < size; i++){
if  (value > array[i])
scoresLessThan++;
}
rank = scoresLessThan/size * 100;
return (int)rank;
}

public double getPercentile(int p){
if (p < 0 || p > 100)
return 0;
if (size <= 0)
return 0;
for (int i=0; i < size; i++){

}

}

public int getSize() {
return size;
}

public double getCapacity() {
return capacity;
}

public String toString() {
String entries = "";
for (int i = 0; i < array.length; i++) {
if (i == array.length - 1)
entries += array[i];
else
entries += array[i] + ", ";
}
return entries;
}

}``````
``````for (int i=0; i < size; i++){
if(getRank(array[i])==p)
return array[i];
}

return 0;
``````