Thread: Complete beginner to Java, problem with error message "non-static variable..."

I'm working on a project for an intro to Java programming class and I've seen other posts about this problem but I don't understand the
terminology of the explanations. This is more than just a hurtle I need to pass to get this program finished, I really want to understand what is going on. What I have for the program is copy and pasted in full and I apologize in advance for whatever errors I may have made.

Thanks in advance for your help!

import java.util.*;
 
import java.lang.*;
 
import java.io.*;
 
 
 
class GemsCFW
 
{
 
    //static MinerCFW Miner1;
 
	//static MinerCFW Miner2;
 
	//static MinerCFW Miner3;
 
 
public static void main (String[] args) throws Exception
{
 
	MinerCFW Miner1, Miner2, Miner3;
 
	String Name, M1, M2, M3;
 
	File test = new File("test.txt");
 
	Scanner reader = new Scanner(test);
 
	//System.out.println(reader.next());
 
	//String Miner1;
 
	//String Miner2;
 
	//String Miner3;
 
	int r, z, i, t, x, y, b;
 
	int r1, r2, r3, s1, s2, s3, e1, e2, e3, g1, g2, g3;
 
	z = 0;
 
	double Percent1, Percent2, Percent3;
 
	//Scanner input = new Scanner(System.in);
 
	MinerCFW Miner1 = new MinerCFW();
 
	MinerCFW Miner2 = new MinerCFW();
 
	MinerCFW Miner3 = new MinerCFW();
 
 
	M1 = reader.next(); //	M1 =	reader.next(); //reset all reader to input
 
	M2 = reader.next();
 
	M3 = reader.next();
 
	Miner1.setName(M1);
 
	Miner2.setName(M2);
 
	Miner3.setName(M3);
 
	for (int count=1; count <= 3; count++)
 
	{
 
		r = reader.nextInt();
 
		z = Miner1.getRubies();
 
 
		{
 
		i = (z + r);
 
		Miner1.setRubies(i);
 
		r = reader.nextInt();
 
		z = Miner2.getRubies();
 
 
		i = (z + r);
 
		Miner2.setRubies(i);
 
		r = reader.nextInt();
 
		z = Miner3.getRubies();
 
 
		i = (z + r);
 
		Miner3.setRubies(i);
 
		r = reader.nextInt();
 
		z = Miner1.getSapphires();
 
 
		i = (z + r);
 
		Miner1.setSapphires(i);
 
		r = reader.nextInt();
 
		z = Miner2.getSapphires();
 
 
		i = (z + r);
 
		Miner2.setSapphires(i);
 
		r = reader.nextInt();
 
		z = Miner3.getSapphires();
 
 
		i = (z + r);
 
		Miner3.setSapphires(i);
 
		r = reader.nextInt();
 
		z = Miner1.getEmeralds();
 
		i = (z + r);
 
 
		Miner1.setEmeralds(i);
 
		r = reader.nextInt();
 
		z = Miner2.getEmeralds();
 
		i = (z + r);
 
 
		Miner2.setEmeralds(i);
 
		r = reader.nextInt();
 
		z = Miner3.getEmeralds();
 
		Miner3.setEmeralds(i);
 
 
		i = (z + r);
 
		}
 
 
		r1 = Miner1.getRubies();
 
		r2 = Miner2.getRubies();
 
		r3 = Miner3.getRubies();
 
		s1 = Miner1.getSapphires();
 
		s2 = Miner2.getSapphires();
 
		s3 = Miner3.getSapphires();
 
		e1 = Miner1.getEmeralds();
 
		e2 = Miner2.getEmeralds();
 
		e3 = Miner3.getEmeralds();
 
 
		g1 = r1+s1+e1;
 
		g2 = r2+s2+e2;
 
		g3 = r3+s3+e3;
 
 
 
		Miner1.setTotal(g1);
 
		Miner2.setTotal(g2);
 
		Miner3.setTotal(g3);
 
 
		x = Miner1.getTotal();
 
		y = Miner2.getTotal();
 
		b = Miner3.getTotal();
 
		t = x+y+z;
 
		Percent1 = x/t;
 
		Percent2 = y/t;
 
		Percent3 = z/t;
 
 
 
		System.out.print(r1);
 
		System.out.print(s1);
 
		System.out.print(e1);
 
		System.out.print(x);
 
		System.out.println(Percent1);
 
 
		System.out.print(r2);
 
		System.out.print(s2);
 
		System.out.print(e2);
 
		System.out.print(y);
 
		System.out.println(Percent2);
 
 
		System.out.print(r3);
 
		System.out.print(s3);
 
		System.out.print(e3);
 
		System.out.print(z);
 
		System.out.println(Percent3);
 
 
		System.out.print("The number of gems found in total is: " +t);
 
	}
 
 
}
 
 
 
 
 
class MinerCFW
 
	{
 
	private String Name;
 
	private int Rubies, Sapphires, Emeralds, Total, r, s, e;
 
 
	public MinerCFW () //had static before void
 
		{ 
 
		  // Rubies = 0;		
		  // Sapphires = 0;
		  // Emeralds = 0;
		  // Name = who;
 
		}
 
	//<<setter methods for ALL the variables 
	public void setRubies (int Rubies1) 
 
		{
 
			Rubies = Rubies1;
 
		}
 
	public void setSapphires (int Sapphires1)
 
		{
 
			Sapphires = Sapphires1;
 
		}
 
	public void setEmeralds (int Emeralds1) 
 
		{
 
			Emeralds = Emeralds1;
 
		}
 
	public void setTotal (int Total1)
 
		{
 
			Total = Total1;
 
		}
 
	public void setName(String who) 
 
		{
 
			Name = who;
 
		}
 
	 //getter for name
	public String getName(String Name) 
 
		{
 
			return Name;
 
		}
 
	//<<getter methods for all the variables 
	public int getRubies () 
 
		{
 
			return Rubies;
 
		}
 
	public int getSapphires () 
 
		{
 
			return Sapphires;
 
		}
 
	public int getEmeralds () 
 
		{
 
			return Emeralds;
 
		}
	public int getTotal()
 
		{
 
			return Total;
 
		}
 
 
	}
 
}

I did not bother to read the gazillion lines of code.

Imagine I have a Person class. Each person has a name. I then create 1000 Person objects. Next I say print name. Which name should it print? However if I say print obj1.name the JVM knows exactly which name to print.

In the above example name would be an instance variable in the Person class. This means that each instance of the class (ie each object) has its own instance of the name variable. Static means it belongs to the class and not an individual object. That means that all objects share the variable. It also means that you can access the variable without create an object at all. The pi variable in the Math class is an example: Math.PI is valid syntax.

I apologize that it is so long, since I didn't know what lines were relevant I didn't know what to omit. Thank you for your response and your explanation. Although I didn't understand some of it I appreciate the help.

If I think I understood you correctly, for each instance of the miner class I created a different identifier (miner1, miner2, ect..). It also sometimes tells me that miner1, miner2, ect.. "might need to be initialized" despite the fact that I created the objects.

there is a rule in java, you can not access non static variables inside a static method. check out your code and either use a non static variable or make the variable static which you are using. It will solve your problem.
for better coding wat i will suggest you is put the whole logic in a separate method and call tht method from main(). Remember as you variables miner1,2 and 3 are not static dont make new method as static.

Thank you so much! I think I may have solved the problem. It now complies. I now have an

Exception in thread "main" java.lang.NullPointerException t GemsCFW.main(GemsCFW.java:66)

error message when I try to run it. The link to the Java Boutique is
exactly what I need for this class and I'm reading it now. Thanks again so much, I really appreciate it.

The code is now

import java.util.*;
 
import java.lang.*;
 
import java.io.*;
 
 
 
class GemsCFW
 
{
 
    //
	static MinerCFW Miner1;
 
	//
	static MinerCFW Miner2;
 
	//
	static MinerCFW Miner3;
 
 
public static void main (String[] args) throws Exception
{
 
	//MinerCFW Miner1, Miner2, Miner3;
 
	String Name, M1, M2, M3;
 
 
	//File test = new File("test.txt");
 
	Scanner input = new Scanner(System.in);
 
	//System.out.println(input.next());
 
	int r, z, i, t, x, y, b;
 
	int r1, r2, r3, s1, s2, s3, e1, e2, e3, g1, g2, g3;
 
	z = 0;
 
	double Percent1, Percent2, Percent3;
 
	//Scanner input = new Scanner(System.in);
 
	//MinerCFW Miner1 = new MinerCFW();
 
	//MinerCFW Miner2 = new MinerCFW();
 
	//MinerCFW Miner3 = new MinerCFW();
 
 
	M1 = input.next(); 
 
	M2 = input.next();
 
	M3 = input.next();
 
	Miner1.setName(M1);
 
	Miner2.setName(M2);
 
	Miner3.setName(M3);
 
	for (int count=1; count <= 3; count++)
 
	{
 
		r = input.nextInt();
 
		z = Miner1.getRubies();
 
 
		{
 
		i = (z + r);
 
		Miner1.setRubies(i);
 
		r = input.nextInt();
 
		z = Miner2.getRubies();
 
 
		i = (z + r);
 
		Miner2.setRubies(i);
 
		r = input.nextInt();
 
		z = Miner3.getRubies();
 
 
		i = (z + r);
 
		Miner3.setRubies(i);
 
		r = input.nextInt();
 
		z = Miner1.getSapphires();
 
 
		i = (z + r);
 
		Miner1.setSapphires(i);
 
		r = input.nextInt();
 
		z = Miner2.getSapphires();
 
 
		i = (z + r);
 
		Miner2.setSapphires(i);
 
		r = input.nextInt();
 
		z = Miner3.getSapphires();
 
 
		i = (z + r);
 
		Miner3.setSapphires(i);
 
		r = input.nextInt();
 
		z = Miner1.getEmeralds();
 
		i = (z + r);
 
 
		Miner1.setEmeralds(i);
 
		r = input.nextInt();
 
		z = Miner2.getEmeralds();
 
		i = (z + r);
 
 
		Miner2.setEmeralds(i);
 
		r = input.nextInt();
 
		z = Miner3.getEmeralds();
 
		Miner3.setEmeralds(i);
 
 
		i = (z + r);
 
		}
 
 
		r1 = Miner1.getRubies();
 
		r2 = Miner2.getRubies();
 
		r3 = Miner3.getRubies();
 
		s1 = Miner1.getSapphires();
 
		s2 = Miner2.getSapphires();
 
		s3 = Miner3.getSapphires();
 
		e1 = Miner1.getEmeralds();
 
		e2 = Miner2.getEmeralds();
 
		e3 = Miner3.getEmeralds();
 
 
		g1 = r1+s1+e1;
 
		g2 = r2+s2+e2;
 
		g3 = r3+s3+e3;
 
 
 
		Miner1.setTotal(g1);
 
		Miner2.setTotal(g2);
 
		Miner3.setTotal(g3);
 
 
		x = Miner1.getTotal();
 
		y = Miner2.getTotal();
 
		b = Miner3.getTotal();
 
		t = x+y+z;
 
		Percent1 = x/t;
 
		Percent2 = y/t;
 
		Percent3 = z/t;
 
 
 
		System.out.print(r1);
 
		System.out.print(s1);
 
		System.out.print(e1);
 
		System.out.print(x);
 
		System.out.println(Percent1);
 
 
		System.out.print(r2);
 
		System.out.print(s2);
 
		System.out.print(e2);
 
		System.out.print(y);
 
		System.out.println(Percent2);
 
 
		System.out.print(r3);
 
		System.out.print(s3);
 
		System.out.print(e3);
 
		System.out.print(z);
 
		System.out.println(Percent3);
 
 
		System.out.print("The number of gems found in total is: " +t);
 
	}
 
 
}
 
class MinerCFW
 
	{
 
	private String Name, who, what;
 
	private int Rubies, Sapphires, Emeralds, Total, r, s, e;
 
 
	public MinerCFW () //had static before void
 
		{ 
 
		  // Rubies = 0;		
		  // Sapphires = 0;
		  // Emeralds = 0;
		Name = what;
 
		}
 
	//<<setter methods for ALL the variables 
	public void setRubies (int Rubies1) 
 
		{
 
			Rubies = Rubies1;
 
		}
 
	public void setSapphires (int Sapphires1)
 
		{
 
			Sapphires = Sapphires1;
 
		}
 
	public void setEmeralds (int Emeralds1) 
 
		{
 
			Emeralds = Emeralds1;
 
		}
 
	public void setTotal (int Total1)
 
		{
 
			Total = Total1;
 
		}
 
	public void setName(String who) 
 
		{
 
			Name = who;
 
		}
 
	 //getter for name
	public String getName(String Name) 
 
		{
 
			return Name;
 
		}
 
	//<<getter methods for all the variables 
	public int getRubies () 
 
		{
 
			return Rubies;
 
		}
 
	public int getSapphires () 
 
		{
 
			return Sapphires;
 
		}
 
	public int getEmeralds () 
 
		{
 
			return Emeralds;
 
		}
	public int getTotal()
 
		{
 
			return Total;
 
		}
 
 
	}
 
 
 
 
}