No output after running the program in java

Question

I need to Create a “main” class called “ParticleDropClass”. The purpose of this class is to contain a calculation of the time it takes for a massive body to fall to the bottom of a vessel containing a viscous liquid.

public class ParticleDropClass {
    double m;
    double d;
    double z;
    double t;
    double v;

    public ParticleDropClass (double x, double y){x=m;y=d;} // creating a constructor 

    public  final double g= 9.81 ;//constants
    public final double  h = 10.0;//constants

    public void drop(double dt ){
        t=0;v=0;
        double  z=h;// intial height at 10m
        while ( z>= 0.0){
            double  a= (d*v*v)/m-g;// formula for body's acceleration
            double dv= a*dt;
            double dz=v*dt ;
            double z1= z+dz;
            double v1= v+dv;
            double t1=t+dt;
            t1=t;
            v1=v;
            z1=z;
        }

        System.out.println("t ="+t +"dt="+t+"s"+ "\n"+"final v="+v+"m/s" );
    }

    public static void main(String[] args) {
        double m=4.3;double d=2.5 ;
        ParticleDropClass b= new ParticleDropClass(m,d);// for an object of               mass 4.3 and 2.5 , at height 0.5 I create a object .
        b.drop(0.5);
    }
}

But I run the above code nothing happens, why?

Also, after everything else I've seen in the answers, you might still get bitten by floating point issues. — Dennis Meng
– Dennis Meng, Commented Aug 8, 2013 at 17:42

keyser · Accepted Answer · 2013-08-08 17:38:36Z

2

You have an infinite loop in drop because the value of z never changes. On a side note I suggest that you fix your indentation and line breaking. It's easily fixed using an IDE such as Eclipse.

I think you meant to write:

z = z1;
t = t1;
v = v1;

and, in the construtor:

m = x;
d = y;

The left operand gets the value of the right operand.

answered Aug 8, 2013 at 17:38

keyser

19.3k16 gold badges62 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

keyser Over a year ago

@RobinPhilip See my edit. It might clear things up. You're assigning values in an incorrect way.

keyser Over a year ago

@RobinPhilip And z++ wouldn't work since you want z to decrease :), maybe z--.

Zhe · Accepted Answer · 2013-08-08 17:38:11Z

1

There are two problems:

In the constructor, you aren't setting m and d, instead, you're setting x and y, which does nothing.

Also, in your while loop, you are not updating the values of t, v and z. Instead, you are just setting your temporary values back to the original.

answered Aug 8, 2013 at 17:38

Zhe

4312 silver badges16 bronze badges

Comments

SimpleJ · Accepted Answer · 2013-08-08 17:38:31Z

1

while ( z>= 0.0)

This is the problem. Your while loop is never altering the variable z, so the loop never ends and never reaches your print statement.

answered Aug 8, 2013 at 17:38

SimpleJ

14.9k13 gold badges62 silver badges98 bronze badges

Comments

rocketboy · Accepted Answer · 2013-08-08 17:40:30Z

1

     public ParticleDropClass (double x, double y){
       x=m;
       y=d;
      }

this is the obvious problem. this does nothing but make x and y 0. May be there are more.

edit

As others have pointed out already, there's an infinite loop in drop.

edited Aug 8, 2013 at 17:40

answered Aug 8, 2013 at 17:35

rocketboy

9,7912 gold badges36 silver badges37 bronze badges

1 Comment

Gene Parmesan Over a year ago

b.drop(0.5) calls the function drop(int) from the main

Sanjeev · Accepted Answer · 2013-08-08 17:38:44Z

0

Looks like you're in an infinite loop. You z (which you're setting to h which is 10) is always greater than or equal to 0.0. You should use better indentation and since I'm pretty sure you're a student, think about using more meaningful identifiers.

answered Aug 8, 2013 at 17:38

Sanjeev

1,5951 gold badge18 silver badges31 bronze badges

Collectives™ on Stack Overflow

No output after running the program in java

5 Answers 5

2 Comments

Comments

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

2 Comments

Comments

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related