error"<identifier> expected" trough the use of interface

[parme]

Hi guys! I have a problem with my project!
I write 4 different class: 1-BankAccount 2-DataSet 3-Tester 4-Measurable. the last is an interface(i'm sorry for my bad english) .
the 4 class are the followings:

public class BankAccount implements Measurable
	{ 

	private double balance;
	private int count_number;
	public BankAccount(int value)
		{ 
		count_number = value; 
		balance = 0;
		}
		
		public BankAccount(int value, double quantity)
		{ 
		count_number = value; 
		balance = quantity;
		}
		
	public void deposit(double amount)
		{
		double newBalance = balance + amount;
		balance = newBalance;
		}
	public void withdrown(double amount)
		{
		if (balance<amount){System.out.println("Valore troppo grande");}
		double newBalance = balance - amount;
		balance = newBalance;
		}
	public double getMeasure()
		{
		return balance;
		}
			
		public double countNumber()
		{
		return count_number;
		}
		
}

public class DataSet
{
    // instance variables - replace the example below with your own
    private double sum = 0;
    private Measurable maximum;
    private int count=0;
    
    public DataSet( Measurable x)
    {
   
    }
    
    public void add(Measurable x)
    {
     sum = sum + x.getMeasure();
     if (sum==0 || maximum.getMeasure()<x.getMeasure() ){maximum = x;}
    }
    public Measurable getMaximum()
    {
    return maximum; 
    }
}

public class Tester
{
 DataSet tester = new DataSet(new BankAccount(0)) ;
 tester.add( new BankAccount(1000) );
 tester.add(new BankAccount(2000) );
 tester.add(new BankAccount(3000));
 Measurable max = tester.getMaximum();
 double n = max.getMeasure();
 
 
}

and the last

public interface Measurable
{
double getMeasure();
}

when i compile BankAccount,DataSet and the interface i find no problem but when i compile the Tester I erceive the following error
"<identifier> expected"
what's wrong?
thanks!

[Fubarable]

Tester has many lines of code just hanging out naked in the class that shouldn't be located where they've been placed. They need to be located inside of a method or constructor or static initializer block or similar beast.

Perhaps you wanted to put those lines in a main method?

[parme]

oh damn! i'm a fool! thanks!:)

[Fubarable]

No problem. Happy coding!