I'm pretty new to Java. I've just written a small example to observe the effects of access modifiers. Maybe the code does not make much sense since I'm just testing things out.

The first code snippet looks like this:

class Tet {
static double a;
double b;
public Tet(double a, double b){
    this.a=a;
    this.b=b;
}

public void get(){
    a=5;
    
}

public static void main(String[] args){
    Tet tet1 = new Tet(2, 5);
    Tet tet2 = new Tet(4, 5);
    System.out.println(tet1.a);
    a=4;
    System.out.println(tet1.a);
    tet1.get();
    System.out.println(tet1.a);
    System.out.println(a);
    
}
}

After this, I made some changes to the code and compiled it again:

class Tet {
static double a;
double b;
public Tet(double a, double b){
    this.a=a;
    this.b=b;
}

public static void get(){
    a=5;
    
}

public static void main(String[] args){
    Tet tet1 = new Tet(2, 5);
    Tet tet2 = new Tet(4, 5);
    System.out.println(a);
    get();
    System.out.println(tet1.a);
    System.out.println(a);
    System.out.println(tet2.a);
    
}
}

After it runs, the cmd looks like this:

but then when wrote Tet tet2 = new Tet(4, 5); the following diagram happened and a was updated with the new value as it's shared :

so both instances of Tet have that variable called a which is shared meaning if you updated a using any of the 2 instance , it's updated in the second instance also.

also in C language, making the variable static means that it's only one instance and also private to the file meaning you can't extern that variable to any other file