CS 100: Lecture L3

February 2

| Back to Lecture Index |

// Example L3A: Odds and Ends

import java.io.*;

public class L3A {
   
   public static void main( String args[]){

      // initialize Text object in to read from standard input.
      TokenReader in = new TokenReader(System.in);
      
      // Example 1.
      // Declaring variables, the type int, assignment statements
      
      int x;
      System.out.println("Enter an integer: "); 
      x = in.readInt();
      int y;
      y = 3;
      int z = x + y;
      x = 2*x + y;
      System.out.println("\nx = " + x + " and z = " + z);
      
      
      // Example 2. 
      // When does a 3-digit number have the same value when digits are written in
      // reverse order?
      
      int n, H, U;
      System.out.println("\n\nEnter a 3-digit integer:");
      n = in.readInt();
      H = n/100;           // Integer division.
      U = n%10;            // The remainder.
      if (H == U)
      { 
         // The value in the ones place and the hundreds place is the same.
         System.out.println("Palindrome");
      }
      else
      {  
         // The value in the ones place and the hundreds place differs.
         System.out.println("Not a palindrome");
      }
      
      
      // Example 3. 
      // For any nonnegative real number a there is a nonegative integer m
      // and a real number r so that a = m*(2pi) + r and 0<=r<2pi. 
      
      double a, m, r;
      a = 20.5;
      m = Math.floor(a/(2*Math.PI));
      r = a - m*2.0*Math.PI;   // Note that r = a % (2.0*Math.PI) does not work.
      System.out.println("\n\n a = " + a + ", m = " + m + ", r = " + r);
      
      
      
      // Example 4.
      // Assign the 13th decimal digit of pi to integer variable d13
      
      double b;
      long bLong;
      int d13;
      
      b = Math.pow(10,13)*Math.PI;
      bLong = (long) b;
      d13 = (int)(b % 10);                // Use long instead of int if very big integers arise.
      System.out.println("\n\nThe 13th decimal in " + Math.PI + " is " + d13);
      
     
      /* The largest value that an int variable can hold is 
                  
                                   2,147,483,647 = 2^31 - 1 about 10^9
                                   
         The largest value that a long variable can hold is 
         
                       9,223,372,036,854,775,807 = 2^63 - 1 about 10^18
      
      */
      
      in.waitUntilEnter();
   }
}

 

// Example L3B: Draws a staircase in two ways

import java.io.*;
import java.awt.*;

public class CUCSDrawing extends Frame
{
    
	final int h0 = 100;
	final int v0 = 50;     // The leftmost step has upper left corner (h0,v0).
	final int delh = 140;   // The tread length.
	final int delv = 70;    // The riser height.
	
	public void paint(Graphics g)
	{
	    int h;
	    int v;
	    
	    // Method 1
	    
	    h = h0;
	    v = v0;
	    
	    g.drawRect(h,v,delh,delv);
	    h = h+delh;
	    v = v+delv;
	    
	    g.drawRect(h,v,delh,delv);
	    h = h+delh;
	    v = v+delv;
	    
	    g.drawRect(h,v,delh,delv);
	    h = h+delh;
	    v = v+delv;
	    
	    // Method 2
	    
	    h = h0;
	    v = v0;
	    int k;
	    for (k=1;k<=3;k=k+1)
	    {
	       g.drawRect(h,v,delh,delv);
	       h = h+delh;
	       v = v+delv;
	    }
	  	
 
    }
	
}

public class L3B
{
	public static void main(String args[])
	{
		CUCSDrawing d = new CUCSDrawing();
		d.resize(1000,800);
		d.move(0,75);
		d.setTitle("L3B");
		d.show();
		d.toFront();
	}
}