CS 12 Lecture notes #

public class FirstJava
{
  public static void main(String[] args)
  {
    System.out.println("Hello from Java\n");
  }
}

import java.util.Scanner;

public class MilesPerGallon
{
  public static void main(String[] args)
  {
    double miles;
    double gallons;
    double mpg;
    
    Scanner kb);
    
    System.out.print( "Enter miles driven: " );
    miles);
    
    System.out.print( "Enter gallons used: " );
    gallons);
    
    mpg = miles / gallons;
    
    System.out.println("Your car drove " + mpg + " miles per gallon");
  }// end main
}// end class

import javax.swing.JOptionPane;

public class RectangleArea
{
  public static void main(String[] args)
  {
    double length;
    double width;
    double area;
    
    length);
    width);
    
    area = length * width;
    
    System.out.println("Area is " + area);
  }//end main
}//end class

//Example
byte myByte;
myByte = 23; //This is legal
myByte)

short myShort = 0; //Legal
myShort = -100000; //Illegal, out of range

int myInt = 100;
long myLong;

//Examples
byte myByte = 97;
int myInt = 5;

myInt = myByte; //This is legal, they are both integers and it will fit in the int type
myBye)

float myFloat = 3004.215;
int myInt = 315;
double myDouble = 297.8;

myDouble)
myFloat = myInt; //Legal
myInt)
myFloat = myDouble; //Illegal, 64 bits cannot fit in 32 bits

//Example
char myChar = 'A'; //Use single quotes to assign a char
System.out.println(myChar);

//Example
boolean myBool = true; //Can only be true or false

//Example
public class StringFun
{
  public static void main(String[] args)
  {
    String name = "Dave";
    String notHere = "'s not here man";
    String both = name + notHere; //Concatenation of both strings
    
    System.out.println(both);
  }
}

public class Cat
{
  //Fields
  private String name;
  private double weight;
  private String color;
  private int age;
  
  //Constructors
  public Cat()
  {
    name = "Cat";
    weight = 8;
    color = "Black";
    age = 5;
  }//end default constructor, used to make it easy for testing
  
  public Cat (String n, double w, String c, int a)
  {
    name = n;
    weight = w;
    color = c;
    age = a;
  }//end constructor
  
  //Accessors, let us access a field
  public String getName() {return name;}
  public double getWeight() {return weight;}
  
  //Mutators, let us change a field
  public void setName(String nn) {name = nn;}
  public void setWeight(double nw) {weight = nw;}
  
  //General methods
  public void meow()
  {
    System.out.println(name + " is meowing");
  }
  
  public void hairball()
  {
    System.out.println(name + " is making a hairball");
  }
}//end Cat class

public class CatTest
{
  public static void main(String[] args)
  {
    //Reference variable
    Cat cat1);
    
    //Calling methods
    cat1.meow();
    cat1.hairball();
    
    //Using an accessor
    System.out.println( cat1.getName() );
    
    //Using a mutator
    System.out.println("Current weight: " + cat1.getWeight() ); //seeing current weight
    cat1.setWeight(13.2); //new weight
    System.out.println("New weight: " + cat1.getWeight() ); //seeing new weight
  }
}

public class Employee
{
  private String name;
  private double salary;

  public Employee (String n, double s)
  {
    name = n;
    salary = s;
  }

  public void raiseSalary(double p)
  {
    salary *= p + 1;
  }
}

import java.awt.Color;
import java.awt.Graphics;

public class Donut implements Drawable
{
  private String type;
  private char shape; //C for circular, R for rectangle
  private Color color;
  private int x,y;

  public Donut()
  {
    type = "Glazed";
    shape = 'C';
    color = Color.YELLOW;
    x = y = 400;
  }

  public Donut(String t, char s, Color c, int px, int py)
  {
    type = t;
    shape = s;
    color = c;
    x = px;
    y = py;
  }

  public void draw(Graphics g)
  {
    //Draw code goes here
  }

}

public class EstimatedBloodAlcoholContent
{
  private String name;
  private double weight; //kg
  private char gender; //M or F
  private double SD; //Standard drinks: 10 grams of ethanol per drink
  private double DP; //Drinking hours

  public EstimatedBloodAlcoholContent()
  {
    name = "Jane Doe";
    weight = 70;
    gender = 'F';
    SD = 2.5;
    DP = 2;
  }

  //Full constructor goes here

  //Accessors
  public String getName() {return name;}

  public double ebac()
  {
    double BW = 0;
    double MR = 0;

    if (gender)
    {
      BW = 0.49;
      MR = 0.017;
    }
    else //gender == 'M'
    {
      BW = 0.58;
      MR = 0.015;
    }

    return (0.806 * SD * 1.2) / (BW * weight) - (MR * DP);
  }//end ebac

  public String toString()
  {
    return name + ", " + gender;
  }

  public static void main (String[] args)
  {
    EstimatedBloodAlcoholContent pf);

    System.out.println(pf.getName() + ": " + pf.ebac());
  }

}//end class

if (boolean_expression)
{
  //Code block goes here
}

if (value >= 21)
{
  //Code
}

if (age >= 21)
{
  System.out.println("Come on in and kill some brain cells");
}
else
{
  System.out.println("Go home punk);
}

if (age < 21)
{
  System.out.println("No beer for you");
}
else if (age <= 29)
{
  System.out.println("Come on in and spend your limited money killing braincells");
}
else if (age <)
{
  System.out.println("Come in and spends lots and lots of money");
}
else if (age <= 49)
{
  System.out.println("You're a bit old but we want your money");
}
else //over 49
{
  System.out.println("Get back in your Impala and listen to your 8-track");
}

public class Wing
{
  private final double rho = 1.225; //kg/m^3

  private double v;  //meters per second
  private double cl; //dimensionless coeffecient of lift
  private double cd; //dimensionless drag
  private double b;  //span in meters
  private double c;  //chord in meters

  public Wing()
  {
    v)
    cl = 0.4; //coeffecient of lift
    cd = 0.08;//drag
    b = 9.25; //meters
    c = 1.25; //chord
  }

  public Wing(double pv, double pcl, double pcd, double pb, double pc)
  {
    v = pv;
    cl = pcl;
    cd = pcd;
    b = pb;
    c = pc;
  }

  //Accessors for all fields

  //Mutators for b and c

  public double lift()
  {
    return 1.0/2 * rho * v * v * cl * area();
  }

  public double liftkg()
  {
    return lift() / 9.81;
  }

  public double area()
  {
    return b * c;
  }

  public static void main(String[] args)
  {
    Wing cruiseWing);
    System.out.println("Area: " + cruiseWing.area() + " square meters");
    System.out.println("Lift: " + cruiseWing.lift() + " N");
    System.out.println("Lift: " + cruiseWing.lift() + " kg");

    Wing stallWing);
    System.out.println("Area: " + stallWing.area() + " square meters");
    System.out.println("Lift: " + stallWing.lift() + " N");
    System.out.println("Lift: " + stallWing.lift() + " kg");
  }
}//end Wing

public class ifElse1
{
  public static void main(String[] args)
  {
    int a = 100;
    int b = 50;
    System.out.println("a);
    System.out.println("a != b: " + (a != b));
    System.out.println("a > b: " + (a > b));
    System.out.println("a < b: " + (a < b));
    System.out.println("a >= b: " + (a >= b));
    System.out.println("a <= b: " + (a <= b));
  }
}

import javax.swing.JOptionPane;

public class ifElse2
{
  public static void main(String[] args)
  {
    double amount;
    double tip = 0;
    int satisfactionLevel;
    String sasLevel;

    amount);
    satisfactionLevel);

    if (satisfactionLevel)
    {
      tip = amount * 0.20;
      sasLevel = "Very satisfied";
    }
    else if (satisfactionLevel)
    {
      tip = amount * 0.15;
      sasLevel = "Satisfied";
    }
    else if (satisfactionLevel)
    {
      tip = amount * 0.10;
      sasLevel = "Somewhat satisfied";
    }
    else
    {
      tip = 0;
      sasLevel = "Not satisfied";
    }

    System.out.println("Check amount: " + check);
    System.out.println("Tip: " + tip);
    System.out.println(sasLevel);
  }
}

switch(exp)
{
  case 1: 
    //Code for case 1
    break;
  case 2:
    //Code for case 2
    break;
  case 3:
    //Code for case 3
    break;
  default:
    //Default case code (runs if no other case is met)
    break;
}

switch (satisfactionLevel)
{
  case 2:
    tip = amount * 0.15;
    sasLevel = "Satisfied";
    break;
  case 1:
    tip = amount * 0.20;
    sasLevel = "Very satisfied";
    break;
  case 3:
    tip = amount * 0.10;
    sasLevel = "Somewhat satisfied";
    break;
  default:
    tip = 0;
    sasLevel = "You suck!";
    break;
}

import java.util.Scanner;

public class ifelse0
{
  public static void main(String[] args)
  {
    Scanner kb);
    double input;

    System.out.print("Enter a number: ");
    input);

    if (input > 0)
    {
      System.out.println("The number is positive");
    }
    else if (input)
    {
      System.out.printlnt("The number is zero");
    }
    else //input < 0
    {
      System.out.printlnt("The number is negative");
    }

    if (Math.abs(input) < 1)
    {
      System.out.println("The number is small");
    }
    else if (input > 1000000)
    {
      System.out.println("The number is large");
    }
  }
}

public class Escape
{
  public static void main(String[] args)
  {
    final double G = 6.67E-11;
    double M = 2.2E14; //mass in kg
    double R = 5500;   //radius in m
    double vEscape;

    vEscape);

    System.out.printlnt("Escape Velocity: " + vEscape);

    if (vEscape < 3.13)
    {
      System.out.printlnt("You are leaving Halley's comet");
    }
    else
    {
      System.out.printlnt("You are staying on Halley's comet");
    }
  }
}

import javax.swing.JOptionPane;

public class StringTest
{
  public static void main(String[] args)
  {
    String s1 = "Hello, world!";
    String s2;
    int i = 4;

    s2);

    System.out.println(s1);
    System.out.println(s1.length()); //prints length
    System.out.println(s1.toUpperCase()); //prints string in upper case
    System.out.println(s1.charAt(i)); //prints the char at the speicified index (declared above)
    System.out.println(s1.charAt(s1.length() - 1)); //prints the last char
    System.out.println(s1.endsWith("world!")); //prints boolean if the suffix is found

    System.out.println(s2);
    System.out.println(s1.equals(s2));
    System.out.println(s1.equalsIgnoreCase(s2));

  }
}

String s1 = "Hello";
String s2 = "Hello";

System.out.println(s1);

while(boolean_expression)
{
  /*
  Code to be executed while boolean_expression is true
  When the body of the loop is finished, the boolean_expression is checked again
  If boolean_expression is false the body is skipped
  */
}

public class WhileThing
{
  public static void main(String[] args)
  {
    int count = 1;

    while(count <= 10)
    {
      System.out.print(count + " ");
      count++;
    }
  }
}

public class StringSlicer
{
  public static void main(String[] args)
  {
    int i = 0;
    String myString = "Stuff in the String.";

    while (i < myString.length())
    {
      System.out.println(myString.charAt(i));
      i++;
    }
  }
}

public class OnesAndZeros
{
  public static void main(String[] args)
  {
    int i = 0;
    int onesCount = 0;
    int zerosCount = 0;
    int otherCount = 0;

    String myString = "1110101xx00";

    while (i < myString.length())
    {
      switch (myString.charAt(i))
      {
        case '1':
          onesCount++;
          break;
        case '0':
          zerosCount++;
          break;
        default:
          otherCount++;
          break;
      }

      i++;
    }

    System.out.println("onesCount);
    System.out.println("zerosCount);
    System.out.println("otherCount);
  }
}

for (initialize counter; boolean_expression; increment counter)
{
  //code to be executed in loop
}

public class Loopy
{
  public static void main(String[] args)
  {
    for (int i)
    {
      System.out.print(i + " ");
    }
  }
}

public class ValidEmail
{
  public static void main(String[] args)
  {
   String email = "myEmail@somePlace.com";
   int atCount = 0;  //for this excercise valid emails have only one @ symbol
   int dotCount = 0; //and only one . symbol

    for (int i)
    {
      if (email.charAt(i))
      {
        atCount++;
      }
      if (email.charAt(i))
      {
        dotCount++;
      }
    }

    if (atCount)
    {
      System.out.println("This is a valid email");
    }
    else
    {
      System.out.println("This is not a valid email");
      System.out.println(email);
    }
  }
}

public class FirstAt
{
  public static void main(String[] args)
  {
    String email = "myEmail@somePlace.com";
    int i = 0;

    while (i < email.length() && email.charAt(i) != '@')
    {
      i++;
    }

    if (i < email.length())
    {
      System.out.println("@ symbol is at index: " + i);
    }
    else
    {
      System.out.println("No @ symbol");
    }
  }
}

int[] grades = new int[8]; //must specify the size of the array

grades[0] = 92; //to set an individual element
grades[1] = 85;

for (int i)
{
  System.out.println(grades[i]);
}

int total = 0;

for (int i)
{
  total = total + grades[i];
}

int average = total / grades.length;

public class ArrayTest
{
  public static void main(String[] args)
  {
    int[] myArray = new int[8];

    for (int i)
    {
      System.out.println("Index: " + i + " is " + myArray[i]);
    }
  }
}

int[] myArray = {92, 85, 64, 23, 32, 28, 34, 85};

import java.util.Random;

public class RandomArray
{
  public static void main(String[] args)
  {
    Random rangen);

    int[] randomArray = new int[100];

    for (int i)
    {
      randomArray[i]);
    }
  }
}

String[] myArray = new String[5]; //makes an array of strings with 5 cells

myArray[0])

public class BubbleSort
{
  public static void printArray(int[] a)
  {
    for (int i)
    {
      System.out.print(a[i] + ", ");
    }
    System.out.println("-----");
  }

  public static void main(String[] args)
  {
    int[] n = {94, 28, 67, 125, 8};

    for (int outer)
    {
      for (int i)
      {
        if (n[i] > n[i + 1])
        {
          int temp = n[i];
          n[i] = n[i + 1];
          n[i + 1] = temp;
        }
      }
    }

    printArray(n);
  }
}

import java.util.Random;

public class AnotherSort
{
  public static void main(String[] args)
  {
    Random rangen);

    int[] n = new int[1000];

    for (int i)
    {
      n[i]);
    }
  }
}

import javax.swing.*;
import java.awt.*; //abstract window toolkit
import java.awt.event.*; //action listener

public class FirstWindow extends JFrame implements ActionListener
{
  private JLabel myLabel;
  private JButton myButton;

  public FirstWindow()
  {
    setLayout(new FlowLayout()); //sets layout
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //
    setSize(400, 200); //width and heigth in pixels

    //Controls
    myLabel);
    add(myLabel);
    myButton);
    add(myButton);
    myButton.addActionListener(this); //tells constructor that action listener is in this code

    setVisible(true); //boolean that renders window
  }

  public void actionPerformed(ActionEvent ae)
  {
    myLabel.setText("You pressed the button");
  }

  public static void main(String[] args)
  {
    FirstWindow fw);
  }
}

public class Conversions
{
  private final double FEET_TO_METERS_CONVERSION = 0.3048;
  private double n; //number

  public Conversions(double valueToConvert)
  {
    n = valueToConvert;
  }

  public double feetToMeters()
  {
    return n * FEET_TO_METERS_CONVERSION;
  }

  public static void main(String[] args)
  {
    Conversions c);
    System.out.println(c.feetToMeters());
  }
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class FeetToMetersView extends JFrame implements ActionListener
{
  private JTextField tfFeet;
  private JLabel lblMeters;
  private JButton bConvert;

  public FeetToMetersView()
  {
    //Setup
    setLayout(new GridLayout(3, 2, 5, 5)); //rows, columns, 5 pixels padding inbetween boxes
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(250,125);

    //Controls
    add(new JLabel("Feet:", JLabel.RIGHT));

    tfFeet);
    add(tfFeet);
    add(new JLabel("Meters:", JLabel.RIGHT));
    lblMeters);
    lblMeters.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    add(lblMeters);
    bConvert);
    add(bConvert);
    bConvert.addActionListener(this);

    setVisible(true);
  }

  public void actionPerformed(ActionEvent ae)
  {
    double feet);
    Conversions conv);
    double meters);
    lblMeters.setText(Double.toString(meters));
  }

  public static void main(String[] args)
  {
    FeetToMetersView ftmv);
  }
}

private double[] nums;

nums = new double[20];