double x = 44.5;
double y = 44.5;

Double xW = new Double(x);
Double yW = new Double(y);

Double dd = new Double(34.239485);

double val = xW.doubleValue();

if (xW < yW)  // can't use < > on class types

if (xW.compareTo(yw) < 0)   // means xW < yW

if (Double.compare(34.2, 23.4) < 0)  

-----------------------------------------------------------

public class StudentID
{
	private String name;
	private int id;

/**** instance methods  ************/

	public void setName(String n)
	{
		this.name = n;  // "this" is optional
	}

	public String getName()
	{
		return name;
	}

	public void setId(int id)
	{
		this.id = id;   // "this" required because same name
	}

	public int getId()
	{
		return this.id;   // "this" is optional
	}

	public String getEmailAccount()
	{
		return "" + this.name.charAt(0) + this.id + "@jhu.edu";
	}

	public boolean isValid()
	{
		return this.id >= 100000 && this.id <= 999999;
	}
}


main 
{ // missing parts

	student = new Student();

	// student.name = name;

	student.setName(name);

	student.setId(stdIn.nextInt());

	while (! student.isValid())
	{
		student.setId(stdIn.nextInt());
	}

	System.out.println(student.getEmailAccount());	
}



public class Test
{
	private int x;			// instance
	private static int y;		// class

	public void doIt()	// instance
	{
	x =1;
	y=2;
	}

	public static void tryIt()  // class
	{
// 	x = 3;  // can't refer to instance data in static method
	y = 4;
	}

	public String toString()
	{
		return x + " " + y;
	}

	public static void main(String [] args)
	{
//		doIt();   // must call with an object
		tryIt();   // ok because in same class as main
		Test t = new Test();
		t.doIt();
//		Test.doIt();  // must call with an object
		Test.tryIt();  // ok from anywhere
		t.tryIt();  // ok, but doesn't make sense

		Test t1;
		Test t2 = new Test();
		t1 = new Test();
		t1.doIt();
		Test.tryIt();
		t2.doIt();

		System.out.println(t1 + " " + t2);
	}

}