Help with program

I am struggling through writing this program that I have started. When I compile it to see if I have everything right java tells me that it cannot find the symbol I defined earlier. If anyone could take a look at my program and give me some advice that would be awesome.

Here it is:
public class CreditCard {

private String number; //The Credit Card number is kept as a string
private boolean valid;

public CreditCard(String n){
number=n;
valid=true;
}

private void check2(){
int v1=Integer.parseInt(number.substring(6,7));
int v1d = v1*2;
if(v1d<=9){
int v1d1 = v1d%10;
(int) v1d2 = v1d/10;
}
else{
int v1d3 = v1d;
}

int v2=Integer.parseInt(number.substring(4,5));
int v2d = v2*2;
if(v2d<=9){
int v2d1 = v2d%10;
(int) v2d2 = v2d/10;
}
else{
int v2d3 = v2d;
}

int v3=Integer.parseInt(number.substring(2,3));
int v3d =v3*2;
if(v3d<=9){
int v3d1 = v3d%10;
(int) v3d2 = v3d/10;
}
else{
int v3d3 = v3d;
}

int v4=Integer.parseInt(number.substring(0,1));
int v4d = v4*2;
if(v4d<=9){
int v4d1 = v4d%10;
(int) v4d2 = v4d/10;
}
else{
int v4d3 = v4d;
}

int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 $
}

}

It helps in cases like this to copy and post the exact and entire compiler message and indicate which line(s) of your code it is referring to.

$ javac CreditCard.java
CreditCard.java:28: cannot find symbol
symbol : variable v1d2
location: class CreditCard
(int) v1d2 = v1d/10;
^
CreditCard.java:28: unexpected type
required: variable
found : value
(int) v1d2 = v1d/10;
^
CreditCard.java:38: cannot find symbol
symbol : variable v2d2
location: class CreditCard
(int) v2d2 = v2d/10;
^
CreditCard.java:38: unexpected type
required: variable
found : value
(int) v2d2 = v2d/10;
^
CreditCard.java:48: cannot find symbol
symbol : variable v3d2
location: class CreditCard
(int) v3d2 = v3d/10;
^
CreditCard.java:48: unexpected type
required: variable
found : value
(int) v3d2 = v3d/10;
^
CreditCard.java:58: cannot find symbol
symbol : variable v4d2
location: class CreditCard
(int) v4d2 = v4d/10;
^
CreditCard.java:58: unexpected type
required: variable
found : value
(int) v4d2 = v4d/10;
^
CreditCard.java:64: cannot find symbol
symbol : variable v4d1
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v3d1
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v2d1
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v1d1
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v4d2
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v3d2
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v2d2
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v1d2
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v4d3
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v3d3
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v2d3
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: cannot find symbol
symbol : variable v1d3
location: class CreditCard
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
CreditCard.java:64: incompatible types
found : java.lang.String
required: int
int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 + v3d3 + v2d3 + v1d3);
^
21 errors

Code:

---

int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3

---

How about using meaningful variable names?

Quote:

---

int c1 = (v4d1 + v3d1 + v2d1 + v1d1 + v4d2 + v3d2 + v2d2 + v1d2 + v4d3 $

---

I guess there's a typo here. But a more fundemental problem exists with the variables v4d1 and the rest.

In general variables have a scope. The scope refers to where in your code you can legally refer to a variable you have declared. (You can't refer to it everywhere; a fact which allows for variables to be reused.) The rule in Java is that once you declare a variable it remains in scope until the } which matches the { of the block where the variable was declared. An example might be clearer:

Code:

---

void someMethod() {
    if(someCondition) { // the "starting" { of foo's block
        int foo = 666;
        if(foo < 10) {
            // some code here
        }
        foo++;
    } // the ending } of the block.  foo is not in scope beyound this point.
    System.out.println(foo); // no! the compiler will not know what the variable foo is supposed to be
}

---

Check that your variables are "in scope". If not you may have to declare them earlier in your code.

You have a multitude of scope issues. Variables declared inside a code block are not visible outside that block. Methods, loops, if statements are all examples of code blocks, Basically anything surrounded by braces { }. You can also have an independent code block.

Code:

---

{ // start of block
    String text = "hello";
}
Sytem.out.println(text); // error

---

Quote:

---

How about using meaningful variable names?

---

Agree. Also it's a good idea to get into the habit of documenting what a method actually does. In this case it could probably be done in just a single sentence.