1. Different-sized integers

   public class MyCode {
      public static void main(String[] args) {
         // Demonstrate the different integer primitive data types
         long  xlMax = Long.MAX_VALUE;
         int   xiMax = Integer.MAX_VALUE;
         short xsMax = Short.MAX_VALUE;
         char  xcMax = Character.MAX_VALUE;
         byte  xbMax = Byte.MAX_VALUE;
   
         long  xlMin = Long.MIN_VALUE;
         int   xiMin = Integer.MIN_VALUE;
         short xsMin = Short.MIN_VALUE;
         char  xcMin = Character.MIN_VALUE;
         byte  xbMin = Byte.MIN_VALUE;
   
         // Note:  you do not yet need to know about "printf" (soon...)
         System.out.printf("%5s %25s %25s\n","type","max","min");
         System.out.printf("%5s %25d %25d\n","long", xlMax,xlMin);
         System.out.printf("%5s %25d %25d\n","int",  xiMax,xiMin);
         System.out.printf("%5s %25d %25d\n","short",xsMax,xsMin);
         System.out.printf("%5s %25d %25d\n","char", (int)xcMax, (int)xcMin);
         System.out.printf("%5s %25d %25d\n","byte", xbMax,xbMin);
      }
   }

2. Floating-point numbers

   public class MyCode {
      public static void main(String[] args) {
         // Demonstrate the different integer primitive data types
         float  xfMax = Float.MAX_VALUE;
         double xdMax = Double.MAX_VALUE;
   
         float  xfMin = Float.MIN_VALUE;  // Not what you may expect!!!
         double xdMin = Double.MIN_VALUE;
   
         // Note:  you do not yet need to know about "printf" (soon...)
         System.out.printf("%5s %25s %25s\n","type","max","min");
         System.out.printf("%5s %25g %25g\n","float",  xfMax,xfMin);
         System.out.printf("%5s %25g %25g\n","double", xdMax,xdMin);
      }
   }

3. Characters

   class MyCode {
     public static void main(String[] args) {
       char c1 = 'A';
       char c2 = (char)66;
       char c3 = "ABCD".charAt(2);
       System.out.println("c1 = '" + c1 + "'");
       System.out.println("c2 = '" + c2 + "'");
       System.out.println("c3 = '" + c3 + "'");
     }
   }

4. Booleans

   class MyCode {
     public static void main(String[] args) {
        boolean b1 = true;
        boolean b2 = false;
        boolean b3 = (b1 && b2);  // b1 AND b2
        boolean b4 = (b1 || b2);  // b1 OR b2
        boolean b5 = !b1;         // NOT b1
        System.out.println("b1 = " + b1);
        System.out.println("b2 = " + b2);
        System.out.println("b3 = " + b3);
        System.out.println("b4 = " + b4);
        System.out.println("b5 = " + b5);
    }
   }

5. integer vs floating-point division

   class MyCode {
     public static void main(String[] args) {
       int i = 10;
       double d = 10;
       System.out.println( 10 / 3 );
       System.out.println(  i / 3 );
       System.out.println(  d / 3 );
       System.out.println( 10 / 3.0 );
       System.out.println(  i / 3.0 );
     }
   }

6. Approximate values of floating-point numbers

   class MyCode {
     public static void main(String[] args) {
       double d1 = (29 / 7.0) * 7.0;
       double d2 = 29;
       System.out.println(d1 == d2);
       System.out.println(d2 - d1);
     }
   }

7. Operator Precedence and Association

   See Figure 2.4 (p. 78)
    

8. Increment and Decrement Operators

   a)  As Statements

   class MyCode {
     public static void main(String[] args) {
       int x = 5;
       System.out.println(x); // 5
       x++;
       System.out.println(x); // 6
       ++x;
       System.out.println(x); // 7
       x--;
       System.out.println(x); // 6
       --x;
       System.out.println(x); // 5
     }
   }

   b)  As Expressions

   class MyCode {
     public static void main(String[] args) {
       int x = 5, y = 0;
       System.out.println(x + "," + y); // 5,0
       y = x++;
       System.out.println(x + "," + y); // 6,5
       y = ++x;
       System.out.println(x + "," + y); // 7,7
       y = 10 + x--;
       System.out.println(x + "," + y); // 6,17
       y = 10 + --x;
       System.out.println(x + "," + y); // 5,15
     }
   }

9. Assignment Operators

   class MyCode {
     public static void main(String[] args) {
       int x = 5;
       System.out.println(x); // 5
       x += 2;
       System.out.println(x); // 7
       x *= 2;
       System.out.println(x); // 14
       x %= 9;
       System.out.println(x); // 5
       x /= 2;
       System.out.println(x); // 2
       x -= 5;
       System.out.println(x); // -3
     }
   }

10. Data Conversion

    a)  Widening (automatic) versus Narrowing (manual, lossy)

    b)  Assignment Conversion

    class MyCode {
      public static void main(String[] args) {
         int a = 5;
         double b = a; // Assignment conversion!  
         System.out.println("a = " + a); // 5
         System.out.println("b = " + b); // 5.0
      }
    }

    c)  Promotion

    class MyCode {
      public static void main(String[] args) {
         int a = 5;
         double b = (2.0 + a); // Promotion!  
         System.out.println("a = " + a); // 5
         System.out.println("b = " + b); // 7.0
      }
    }

    d)  Casting

    class MyCode {
      public static void main(String[] args) {
         double a = 5.0;
         int b    = a; // Will not compile!
         System.out.println("a = " + a);
         System.out.println("b = " + b);
      }
    }

    So we cast the double into an int:

    class MyCode {
      public static void main(String[] args) {
         double a = 5.0;
         int b    = (int) a; // Casting!
         System.out.println("a = " + a); // 5.0
         System.out.println("b = " + b); // 5
      }
    }

    Note that casting truncates:

    class MyCode {
      public static void main(String[] args) {
         int a = (int)5.9;
         int b = (int)-5.9;
         System.out.println("a = " + a); // 5
         System.out.println("b = " + b); // -5
      }
    }

11. More on the Scanner

    a)  From p. 87:  Just need to know the methods next***()
    next(), nextLine(), nextBoolean(), nextByte(), etc...

    b)  next() versus nextLine()
    
    Does not work quite as you might expect:
      * next returns next input token as a String
      * nextLine returns the rest of the current line as a String
      * they do not mix-and-match well!

    class MyCode {
      public static java.util.Scanner scanner = new java.util.Scanner(System.in);
      public static void main(String[] args) {
         String s1, s2;
         System.out.print("Enter a few words: ");
         s1 = scanner.next();
         System.out.print("Enter a few other words: ");
         s2 = scanner.nextLine();
         System.out.println("s1 = '" + s1 + "'");
         System.out.println("s2 = '" + s2 + "'");
      }
    }

    Do this again, but just use next, not nextLine:

    class MyCode {
      public static java.util.Scanner scanner = new java.util.Scanner(System.in);
      public static void main(String[] args) {
         String s1, s2, s3;
         System.out.print("Enter a few words: ");
         s1 = scanner.next();
         s2 = scanner.next();
         s3 = scanner.next();
         System.out.println("s1 = '" + s1 + "'");
         System.out.println("s2 = '" + s2 + "'");
         System.out.println("s3 = '" + s3 + "'");
      }
    }

    Once more, but just use nextLine, not next:

    class MyCode {
      public static java.util.Scanner scanner = new java.util.Scanner(System.in);
      public static void main(String[] args) {
         String s1, s2;
         System.out.print("Enter a few words: ");
         s1 = scanner.nextLine();
         System.out.print("Enter a few other words: ");
         s2 = scanner.nextLine();
         System.out.println("s1 = '" + s1 + "'");
         System.out.println("s2 = '" + s2 + "'");
      }
    }

Graphics
 

1. Applet  vs  Application
    
2. Writing graphics code in an Application:  BasicGraphics.java

   // BasicGraphics.java
   
   // A simple shell for drawing graphics as described in our textbook.
   // Note that this is an *application* whereas the book uses *applets*.
   // This should have little impact on you, however.
   
   import java.awt.*;
   import java.awt.event.*;
   import java.util.*;
   import javax.swing.*;
   
   public class BasicGraphics extends JComponent {
      
      public static void main(String[] args) {
         JComponent myGraphics = new BasicGraphics(); // Your class name goes here!
         launch(myGraphics, 500, 300); // Set the initial dimensions here!
      }
      
      public void paint(Graphics page) {
         int width = getWidth();
         int height = getHeight();
   
         // paint a blue rectangle as large as the window      
         page.setColor(Color.blue);
         page.fillRect(0,0,width,height);
         
         // paint a yellow oval inscribed in the blue rectangle
         page.setColor(Color.yellow);
         page.fillOval(0,0,width,height);
      }
   
      //////////////////////////////////////////////////////////////////////////////
      /////////////////           END OF YOUR CODE             /////////////////////
      /////////////////  (you may ignore all the code below!!! /////////////////////
      //////////////////////////////////////////////////////////////////////////////
   
      public static void launch(JComponent jc, int width, int height) {
         JFrame frame = new JFrame(jc.getClass().getName());
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         JPanel cp = new JPanel();
         cp.setLayout(new BorderLayout());
         cp.add(jc);
         frame.setContentPane(cp);
         frame.setSize(new Dimension(width,height));
         frame.setVisible(true);
      }
   }

3. More Graphics:  BasicGraphicsDemo1.java
   
   // BasicGraphicsDemo1.java
   
   // A demo of some simple graphics operations, starting from BasicGraphics.java
   
   import java.awt.*;
   import java.awt.event.*;
   import java.util.*;
   import javax.swing.*;
   
   public class BasicGraphicsDemo1 extends JComponent {
     
      public static void main(String[] args) {
         JComponent myGraphics = new BasicGraphicsDemo1(); // Your class name goes here!
         launch(myGraphics, 500, 300); // Set the initial dimensions here!
      }
     
      public void paint(Graphics page) {
         int width = getWidth();
         int height = getHeight();
   
         // filled blue rectangle as large as the window     
         page.setColor(Color.blue);
         page.fillRect(0,0,width,height);
        
         // filled yellow oval inscribed in the blue rectangle
         page.setColor(Color.yellow);
         page.fillOval(0,0,width,height);
        
         // unfilled (drawn) black rectangle on the left
         page.setColor(Color.black);
         page.drawRect(10,10,width/2-20,height-20);
        
         // unfilled thick-lined black ovals on the right
         ((Graphics2D)page).setStroke(new BasicStroke(5)); // 5 pixels wide
         page.drawOval(width/2+10,10,width/2-20,height/2-20);
         page.drawOval(width/2+10,height/2+10,width/2-20,height/2-20);
   
         // unfilled thin-lined red triangle on the right
         ((Graphics2D)page).setStroke(new BasicStroke(1)); // set back to 1 pixels wide
         page.setColor(Color.red);
         Polygon p1 = new Polygon();
         p1.addPoint(3*width/4,height/3);  // addPoint(x,y)
         p1.addPoint(width/2+40,2*height/3);
         p1.addPoint(width-40,2*height/3);
         page.drawPolygon(p1);
        
         // filled green pentagon in the middle
         page.setColor(Color.green);
         int pWidth = width/5;
         int pHeight = height/10;
         int pLeft = width/2  - pWidth/2;
         int pTop  = height/2 - pHeight/2;
         Polygon p2 = new Polygon();
         p2.addPoint(pLeft           , pTop);
         p2.addPoint(pLeft+pWidth/3  , pTop+pHeight);
         p2.addPoint(pLeft+2*pWidth/3, pTop+pHeight);
         p2.addPoint(pLeft+pWidth    , pTop);
         page.fillPolygon(p2);
        
         // custom-colored red rectangles in the middle
         page.setColor(new Color(100, 0, 0));  // RGB (Red, Green, Blue)
         page.fillRect(width/2-10, 10, 30, 30);
         page.setColor(new Color(200, 25, 25));
         page.fillRect(width/2-10, 50, 30, 30);
         page.setColor(new Color(255, 50, 50));
         page.fillRect(width/2-10, 90, 30, 30);
        
         // using trig to place a small blue circle at 70 degrees
         // in the first quadrant of an orange circle
         int radius = 50;
         page.setColor(Color.orange);
         // oval will be centered at (100,100)
         page.fillOval(100-radius,100-radius,2*radius,2*radius);
         // here we use 70 degrees
         int blueCenterX = 100 + (int)(radius*Math.cos(Math.PI*70/180));
         int blueCenterY = 100 - (int)(radius*Math.sin(Math.PI*70/180));
         int blueRadius = radius/10;
         page.setColor(Color.blue);
         page.fillOval(blueCenterX-blueRadius,blueCenterY-blueRadius,
                       2*blueRadius,2*blueRadius);
                      
         // draw a line connecting the centers of the orange and blue circles
         page.drawLine(100,100,blueCenterX,blueCenterY);
      }
   
      //////////////////////////////////////////////////////////////////////////////
      /////////////////           END OF YOUR CODE             /////////////////////
      /////////////////  (you may ignore all the code below!!! /////////////////////
      //////////////////////////////////////////////////////////////////////////////
   
      public static void launch(JComponent jc, int width, int height) {
         JFrame frame = new JFrame(jc.getClass().getName());
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         JPanel cp = new JPanel();
         cp.setLayout(new BorderLayout());
         cp.add(jc);
         frame.setContentPane(cp);
         frame.setSize(new Dimension(width,height));
         frame.setVisible(true);
      }
   }
    

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