I'm creating a Java code and it keeps going back and forth between 2 errors >

Error #1:

TestClass.java:26: error: non-static method isEmpty(LetterInventory) cannot be referenced from a static context

Error #2:

TestClass.java:26: error: method isEmpty in class LetterInventory cannot be applied to given types; if(v.isEmpty()) { ^ 

There are 2 Java files causing the conflict: File #1 LetterInventory (compiles without issue) and File #2 TestClass (the one getting the error codes).

The first error code results from these programs:

I have code from 2 separate Java files that are conflicting.

File #1:

 public int size() { return size; } public boolean isEmpty(LetterInventory p) { if(size == 0) { return true; } return false; }

File #2:

 String insert = scan.next(); LetterInventory v = new LetterInventory(insert); if(LetterInventory.isEmpty(v)) {

I changed File #2 up SLIGHTLY, and that's when I got the 2nd error code:

New File #2:

 public static void main (String[] args) { System.out.println("This is to the Letter Inventory!"); System.out.println("Please type a word of one or more characters: "); String insert = scan.next(); LetterInventory v = new LetterInventory(insert); if(v.isEmpty()) { System.out.println("Please include at least one character."); insert = scan.next(); v = new LetterInventory(insert); }

Please help! If you could also give an example of what would work in the code, that would be amazing