How to call an array from a static method? - arrays

Question

In this code, how do I call an array globally for other methods to use?
Background info on my code, we are asked to scan a file that contains DNA strands then translating it to an RNA Strand.
I receive the error: " cannot find symbol - variable dna " when i call the dna array on the translation method (it can't find dna.length) for(int i=0; i < dna.length; i++){
public class FileScannerExample
{
public static void main(String[] args) throws IOException
{
//This is how to create a scanner to read a file
Scanner inFile = new Scanner(new File("dnaFile.txt"));
String dnaSequence = inFile.next();
int dnalength = dnaSequence.length();
String[] dna = new String[dnalength];
for(int i=0; i<=dna.length-2 ; i++)
{
dna[i]=dnaSequence.substring(i,i+1); //looking ahead and taking each character and placing it in the array
}
dna[dna.length-1]=dnaSequence.substring(dna.length-1); //reading the last spot in order to put it in the array
//Testing that the array is identical to the string
System.out.println(dnaSequence);
for(int i = 0 ; i<=dna.length-1; i++)
{
System.out.print(dna[i]);
}
}
public void translation()
{
for(int i=0; i < dna.length; i++){
//store temporary
if (dna[i] = "A"){
dna[i] = "U";
}
if(dna[i] = "T"){
dna[i] = "A";
}
if(dna[i] = "G"){
dna[i]= "C";
}
if(dna[i] = "C"){
dna[i] = "G";
}
}
}
}

Answer 1

you need to bring the symbol into scope before you can reference it. you can do this, either by pulling it up into a higher scope (as a field in the class), or by sending it into the local scope by passing it as a method parameter.
As a class member:
public class Test
{
private String myField;
void A() {
myField = "I can see you";
}
void B() {
myField = "I can see you too";
}
}
As a method parameter:
public class Test
{
void A() {
String myVar = "I can see you";
System.out.println(myVar);
B(myVar);
}
void B(String param) {
param += " too";
System.out.println(param);
}
}
Note that in order to see an instance member, you must be referencing it from a non-static context. You can get around this by declaring the field as static too, although you want to be careful with static state in a class, it generally makes the code more messy and harder to work with.