Static code doesn't work for me in Java

Question

I am pretty sure that I have done something similar in the Static lesson, but I always get errors.

public class Program
{
public class Landmark {
public static int DEPTH;
// String recordNo = "a";
// public String getRecordNo() {
// return recordNo;
// }
// public void setRecordNo(String a){
// this.recordNo = a;
// return a;
// }
Landmark(){

DEPTH--;
}
}

public static void main(String[] args) {
System.out.println("Hello World!");
Landmark.DEPTH = 0;
Landmark k = new Landmark();
Landmark l = new Landmark();
System.out.println(Landmark.DEPTH);
}
}

Answer 1

move the landmark class outside of the program class
inner classes cant declare static variables unless they are also constant(i think)

Answer 2

Write the question related to your problem and I will surely solved it.