//-----------------------------------------------------------------------------
// ball0 2/16/2000 T.Yan, DIS
// This example is deliberately over-commented to help explain
// some of the programming concepts.
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// class Ball is the class used to instantiate a ball object 
// in the main class
//-----------------------------------------------------------------------------
class Ball {
    char name;
    double pos;
    double vel;
} // class Ball

//-----------------------------------------------------------------------------
// ball0 is the target for main class
// Don't mix up the names ball0 and ball!
//-----------------------------------------------------------------------------
public class ball0 {
    public static void main(String[] args) {
	
	//---------------------------------------------------------------------
	// Allocate and assign a ball object
	//---------------------------------------------------------------------
	Ball a = new Ball();

	//---------------------------------------------------------------------
	// Customize each run
	//---------------------------------------------------------------------
	TokenReader in = new TokenReader(System.in);
	do {
	    System.out.print("Enter initial pos:  "); 
	    a.pos = in.readDouble();
	    if(a.pos < 0) System.out.println("Wrong!");
	} while(a.pos < 0);
	// should account for other kinds of limitations....
	System.out.print("Enter initial vel:  "); 
	a.vel = in.readDouble();
	System.out.print("Enter acceleration: "); 
	double accel = in.readDouble();

        a.name = '*';   // Icon to draw

	//---------------------------------------------------------------------
        // Repeated move and draw balls limit=100 times
	// Think of each loop as "1 second" of time passing
	//---------------------------------------------------------------------
	int limit = 100; // target number of moves
	int moves = 0;   // number of moves performed
	while (moves < limit) {

	    //-----------------------------------------------------------------
	    // Print ball
	    //-----------------------------------------------------------------
	    for (int i = 0; i < a.pos; i++)
		System.out.print(" ");    // Print blanks
	    for(int s=0; s < 1e6; s++);   // Introduce a "pause" to slow output
	    System.out.print(a.name);     // Print ball at current pos
	    System.out.println();         // Advance output for new pos

	    //-----------------------------------------------------------------
	    // Move ball
	    // Slight problem -- ball cannot go "below ground"!
	    // When the ball hits, assume a completely elastic collision.
	    // So, the ball will bounce in the opposite direction with the
	    // same velocity.
	    //-----------------------------------------------------------------
	    a.pos = a.pos + a.vel + accel/2.0;
	    a.vel = a.vel + accel;
	    if (a.pos <= 0) {     // hit or went "below ground"
		a.vel = -a.vel;   // change dir of vel
	    }

	    //-----------------------------------------------------------------
	    // Recall that the ball stops bouncing after reaching the
	    // target number of moves.
	    //-----------------------------------------------------------------
	    moves++;

	}

    } // method main

} // class ball0