2) public class Hi { //Hi has to match exactly the filename Hi.java (case sensitive)

public static void main(String[] args) { //This is the "main" function of the program. All my code goes inside it.

System.out.println("Hello, World!");

//TODO: Make some text-based graphics for this programSystem.out.println("can you make \"java\" \\ C++ run other programs?");System.out.println("//Yes!");

int myInteger; //defining (declaring) a variable.//This lets Java know that we want a variable that holds integers,//and is named myInteger.

int MyInteger; //variables are case sensitive, so this is//a different variable than the one declared above.

myInteger = 72; //stores 72 in the myInteger variable.myInteger = 36; //reassign the variable's value.

myInteger = myInteger + 6; //myInteger becomes 6 greater than what it is currently

int zero; //define a second variable.zero = 1; //assign it zero.

System.out.println(myInteger / 3); //some basic arithmetic

int v = (int)(Math.random() * 10); //random number from 0 through 9.999..., truncated to an integer.

System.out.println(v); //print out the random number (now 0 through 9, since truncated).

}}

//We've seen://==========//single line comments

//how to print stuff

//Strings (a sequence of characters; we can define one by surrounding text in quotes)//Escape characters (how to get a quote or backslash in there)

//Variables//Case sensitive names//Every variable has a type.//Think of them as boxes that have contents (that can change over time).//The = means "gets" or "becomes".

//Java compiler is used to convert .java files to .class files (bytecode)

//3 types of errors are possible in Java://Syntax error: Not a legal Java program. ALWAYS caught by the compiler!//Runtime error: Not caught by the compiler, but is caught during runtime.//Semantic (logic) error: Not caught by the computer at all. Program just does the

wrong thing,//or otherwise behaves badly!

3)//A basic Java application.public class Hello {

public static void main(String[] args) {System.out.println("Hello CS120 class!");

}}

// Character escape sequences://// \t Insert a tab in the text at this point.// \b Insert a backspace in the text at this point.// \n Insert a newline in the text at this point.// \r Insert a carriage return in the text at this point.// \f Insert a formfeed in the text at this point.// \' Insert a single quote character in the text at this point.// \" Insert a double quote character in the text at this point.// \\ Insert a backslash character in the text at this point.

4)public class VariableTest {

public static void main(String[] args) {//Any variable declaration consists of the//type followed by the variable name and a semicolon

int myVariable; //integer variabledouble salary; //double variable (decimals allowed)boolean havingGoodDay; //boolean means true or false.

salary = 100000.43; //changing the value of a variable.System.out.println(salary); //printing the variable out to console

salary = salary * 1.05; //salary becomes whatever it was times 1.05 (a 5% raise)

System.out.println(salary); //printing the variable out to console (different value now)

//The 5 arithmetic operators in Java:// * multiplication// / division// - substraction// + addition// % modulo (remainder after division)

myVariable = 33;int d = 5;

System.out.println(myVariable / d); //integer division truncates the remaindersalary = 33;System.out.println(salary / 5); //double (floating point) division gets what

you'd expect.

havingGoodDay = true; //boolean variables can only take on the values true or false.

System.out.println(havingGoodDay);

//Naming conventions in Java://variable names always start with a lowercase first letter.//If there are several words, we squish them all together//and use a capital letter on each subsequent word.

//Javadocs are online documentation for Java features.

System.out.println(Math.sqrt(2.0)); //prints out square root of 2.

//order of operations://First: *, / and % from left to right.//Then: + and - from left to right.

double firstRoot = (-2 + Math.sqrt(2*2 - 4*3*(-1))) / (2*3);double secondRoot = (-2 - Math.sqrt(2*2 - 4*3*(-1))) / (2*3);

System.out.println("The first root is: "+firstRoot);System.out.println("The second root is: "+secondRoot);

//Verify this is right (should be zero).System.out.println(3*Math.pow(firstRoot, 2) + 2*firstRoot - 1);System.out.println(3*Math.pow(secondRoot, 2) + 2*secondRoot - 1);

}}

4b)//Name: whole CS120 class.//Approximate time to complete: 20 minutes.//References used: Java API documentation.

//Java API documentation: http://download.oracle.com/javase/1.5.0/docs/api///The Math class: http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Math.html

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

double a = Math.random();

System.out.println(a);System.out.println(a);

if (a > .5) {System.out.println("hello");

}

if (a <= .5) {System.out.println("goodbye");

}

double b = Math.round(a*10);System.out.println(b); //random number from 0 to 10 (not as much chance as

getting 0 or 10 though).System.out.println(b / 10); //random number from 0 to 1, in .1 increments.

//dice rolling.//We will rolla "2d6" (in D&D notation) meaning rolling the six-sided die

twice.double dieRoll1 = Math.random() * 6;dieRoll1 = Math.floor(dieRoll1) + 1;System.out.println("Die roll is:" + dieRoll1);

double dieRoll2 = Math.random() * 6;dieRoll2 = Math.floor(dieRoll2) + 1;System.out.println("Die roll is:" + dieRoll2);

}

}

4c)//Name: whole CS120 class//Time to complete: 30 minutes//Resources used: None

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

double a;double b;double c;

//integer division truncates any fractions (gives you an int back!)a = 4.0 / 7.0;b = -3.0 / 2;c = -120;

if (b*b - 4*a*c >= 0) {//double is a type for decimal numbers (like 3.8, -9.999, etc.)double root1;

//Math.sqrt() is a function. Put the input (called the argument) inside

//the parentheses.//Order of operations *, /, +, - same as in algebra:

//* and / first from left to right.//then + and - from left to right.

root1 = (-b + Math.sqrt(b*b - 4 * a * c)) / (2*a);

System.out.println(root1);

//"roundoff error" happens with decimals ("double" values).System.out.println( a*root1*root1 + b*root1 + c); //we expect ths to be

0.

double root2;root2 = (-b - Math.sqrt(b*b - 4 * a * c)) / (2*a);

System.out.println(root2);

System.out.println( a*root2*root2 + b*root2 + c); //we expect ths to be 0.

//The + operator either means "add" or "concatenate", depending on context.

//If one of the inputs is a "string", then it concatenates (puts together).

System.out.println("The first root is " + root1 + " and the second is " + root2);

}

if (b*b - 4*a*c < 0) {System.out.println("There are no real roots");

}}

}

6)import java.util.*; //This tells Java that we will use classes//from the java.util package (on your computer).//Without this, I'll get an error when trying to make a Scanner object//(Scanner resides in the java.util package).

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

//Types in Java://primitives (int, double, boolean)...there are only 8 primitives.//classes (String, Scanner)...there are tons of classes (and we can make our

own).

//Primitive values are just pieces of data (e.g. 1, false, -3.8).//Class values are called "objects". They consist of data *and*//operations that can be performed on that data (called "methods").

//Creates a Scanner object, stores it in the userInput variable.Scanner userInput = new Scanner(System.in);

//String is a class as well. This is really what we are using//when we put double quotes around a phrase. For example:String u = "Say something!";System.out.println(u);

//Let's get a String from the user.//nextLine is a "method" available for Scanner objects.//It's basically a that//gets a String from the user.String t = userInput.nextLine();System.out.println("You said: "+t); //...and echo it back to them.

System.out.println("What's your favorite number?");

//let's get an int from the user.int favoriteNumber;favoriteNumber = userInput.nextInt();

System.out.println("Your fav # is "+favoriteNumber);

System.out.println("Say true or false.");//get a true or false value from the user.boolean f = userInput.nextBoolean();

//This is an "if statement". It lets us//select what code to execute based on some//conditions (in this case, whether f is true or false).if (f) {

//If f is true,//this code block will be executedSystem.out.println("You said true");

}else {

//If f is is not true (i.e. false),//this code block will be executedSystem.out.println("You said false");

}

}}

6b)import java.util.*; //let's us use the Scanner package//The * means import every class in that package.

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

//Data types: int, double, long.//double

//roundoff error. (about 15 digits of accuracy)//int

//integers only. less range. no roundoff error.//long

//like an int, but has more precision.//boolean

//true and false are the only possibilities.

//local variable pi - the caps one is a static variable.double pi;pi = Math.PI; //how you use a static variable: name of of the class, a dot,

and the name of the variable.

System.out.println(pi);

//Step 0) import the package in which the class exists (see top of this program for import statement for Scanner).

//Step 1) Create a variable to store the object in.Scanner myInput; //defines a variable called myInput, capable of holding a

Scanner object

//Step 2) Create a new object and store it into the variable.//This is called a constructor call (see javadocs)

//Step 3) Use it, by calling methods.myInput = new Scanner(System.in);

String t; //defining a new variable

while(0 < 1) { // (0 < 1) is always true, so this loop goes forever.System.out.println("What's your name?");t = myInput.nextLine(); //calling a method to get a line of input from

the user.

//get rid of leading and trailing space.t = t.trim();

//capitalize the first letter, and lowercase the rest.String firstLetter;String theRest;firstLetter = t.substring(0, 1);theRest = t.substring(1);

firstLetter = firstLetter.toUpperCase();theRest = theRest.toLowerCase();

System.out.println("Hi, " + firstLetter + theRest + ".");

//tell them how many letters are in their name.int nameLength;nameLength = t.length();System.out.println("your name is " + nameLength + " characters long");

System.out.println("What's the radius of your circle?");String radiusString = myInput.nextLine();double r = Double.parseDouble(radiusString);

//Note that Double is a class, but double is a primitive.//Here we are calling a *static* method on the class to convert to a

*double*.System.out.println("The circumference of your circle is " + 2 * Math.PI

* r);

double rSquared = Math.pow(r, 2);System.out.println("The area of your circle is " + Math.PI * rSquared);

System.out.println("In terms of PI, the circumference of your circle is " + 2*r + " * pi");

}

}}

Good Class demos for using methods of static classes:

http://cs.nmu.edu/~mkowalcz/cs120f10/notes/08/section%203/

7) import java.util.*;

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

//System.in is the raw input stream from the console//so that's always going to be the same// (you could change it to a file though - we'll see// how later in the semester)Scanner in = new Scanner(System.in);

System.out.println("How old are you?");

int age = in.nextInt();

//Exactly one of these 4 main blocks will be executed.if (age <= 3) {

System.out.println("Too young!");

//A nested if. If the age is at most 3, then//exactly one of these 2 blocks will be executed.if (age < 1) {

System.out.println("Hey Baby!");}else {

System.out.println("Hey toddler!");}

}else if (age < 10) {

System.out.println("You're ok");}else if (age < 18) {

System.out.println("grow up");}else {

System.out.println("get a job!");

}

//if statement without "else if" or even an "else".if (age > 120) {

System.out.println("Way to old! You are probably lying.");}

if (age < 10 && age >= 0) { //This && means "and"System.out.println("You are a single digit person.");

}

//"or" means logical or. (one or the other or both)if (age < 0 || age > 120) {

System.out.println("I find this unlikely.");}

int salary;if (age < 18) {

salary = 0;}else {

salary = 50000;}

System.out.println("Your salary is " + salary);

// ! is the negation operator (the "not" operator)if ( !(salary > 250) ) {

System.out.println("You aren't making much");}

if (salary == 100000) {System.out.println("You're rich");

}

}}

8)import java.util.*;

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

//Scanner is an example of a "class".//primitive values (3.4, true, -5) - they're just a plain old value.//class values (e.g. the thing that's inside my s variable below)//are called objects.Scanner s = new Scanner(System.in);

//we are calling an action on our scanner object (the action is//called a "method" and this method just happens to be called nextInt).int i = s.nextInt();

//3 is less than 7, so b gets the value: true.boolean b = (3 < 7);

System.out.println(b); //prints true

if (3 < 7) {int j = 5; //only has scope for this code block (the rest of//the if statment)

System.out.println("yes, 3 < 7.");}

//j = 2; //uncommenting this line would cause a compile time error.//j does not have scope down here since it's declared inside the if//statement block.

}}

9)import java.util.*;

//nextInt, nextDouble, and nextBoolean only take as many characters//of input as necessary to satisfy your request (this may or may not//contain newline characters). nextLine always returns the//rest of the current line where the Scanner left off, and//throws away the newline character.

//Therefore, if we're only interested in taking one piece//of input per line, we just need to make a call like this:// doctorWho.nextLine();//...after every nextInt (the same thing// applies for nextDouble and nextBoolean). This way we will//never go wrong.

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

Scanner doctorWho = new Scanner(System.in);//You only ever want to create one Scanner//for user input. If you create multiple ones,//they will fight each other.

System.out.println("Your favorite number, please?");int i = doctorWho.nextInt();

System.out.println("oh yeah, mine is " + (i+1) );

double d = doctorWho.nextDouble();

System.out.println(d);

System.out.println("... and the Doctor's name?");

doctorWho.nextLine(); //eat up the rest of the previous line!String doctor = doctorWho.nextLine();System.out.println("The doctor's name is: "+doctor);

}}

9c)import java.util.*;

//Attempt at a hangman program.public class GuessTheWordGame {

public static void main(String[] args) {//Create a scanner.Scanner myInput;myInput = new Scanner(System.in);

//Ask player one for the secret word.System.out.println("What's your secret *secret* word?");String secret;secret = myInput.nextLine();

//Print out some space so player 2 doesn't see it.int index = 0;while(index < 40) {

System.out.println();index = index + 1;

}

int guessesLeft; //number of guesses leftguessesLeft = 12;//as long as we have guesses left.while (guessesLeft > 0) {

//Ask player two to guess a letter or phraseSystem.out.println("PLayer 2: guess a letter or phrase please.");System.out.println(guessesLeft + " guesses left.");

String guess = myInput.nextLine();

//Say whether or not that letter (or phrase) was in the word.boolean good;good = secret.contains(guess);

if (good == true) {System.out.println("Yes, it contains "+ guess +"!");

}else {

System.out.println("No, it doesn't contains "+ guess +"!");guessesLeft = guessesLeft - 1;

}}

//Print game overSystem.out.println("Game over");

}}

9d)import java.util.*;

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

int count = 0; //shorthand for the two lines: int count; and count = 0;

//the while loop will repeat the code block after it//as long as the boolean condition in the () is true.while(count < 5) {

System.out.println("Damon is cool.");System.out.println(count);count = count + 1;

}

//for loop - it's sort of a shorcut way of doing a common kind of loop pattern. We will see more of these later.

for(int i = 0; i < 1000; i = i + 1) {

System.out.println(i);}

//count up to 30000, print out a message and pause at every multiple of 10,000int i = 0;while(i <= 30000) {

System.out.println(i);if (i % 10000 == 0) {

System.out.println("We got to a multiple of ten-thousand!");

//don't worry about exceptions - we haven't covered this part.try {

Thread.sleep(1000); //1000 milliseconds = 1 second.}catch(Exception e) {}

}

i = i + 1;}

//This loop won't do anything (because i is already bigger than 100).while(i < 100) {

System.out.println("We got down here");}

Scanner myInput = new Scanner(System.in); //creates the scanner

int age;do {

System.out.println("What's your age?");String s;s = myInput.nextLine();age = Integer.parseInt(s);

}while(age < 0);

if (age < 0) {System.out.println("liar!"); //this should never end up getting

executed, because of the do..while loop above.}else if (age < 5) {

System.out.println("how did you get this to compile??");}else if (age < 13) {

System.out.println("Go back to your homework.");}else if (age < 21) {

System.out.println("To young to drink.");}else {

System.out.println("Older gentleman / woman.");}

}

}

10a)public class Example2 {

public static void main(String[] args) {//here is one way of truncating to two decimal placesdouble d = 33.2482;int i = (int)(d*100);System.out.println(i / 100.0);

//here is a way of formatting to two decimal places for outputd = 33.2482;System.out.printf("%1.2f", d);System.out.println(); //need this println, since printf doesn't//produce a newline character

//Note that the first way truncated the extra digits//and the second way rounded them.

}}

10b)public class InterestingStringThing {

public static void main(String[] args) {int i = 5;int j = 6;

//This next line has a logical error. Java//will concatenate the string with i, and then//the resulting string is concatenated with j,//resulting in 56.System.out.println("The sum is "+i+j);

//This way gets the right result. Using parenthesis//forces the addition to occur first, and since//both arguments (i.e. inputs) are int values,//the result is an int value.System.out.println("The sum is "+(i+j));

}

}

10c)import java.util.*;

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

int i = 10;

//count from 10 down to 0.while(i >= 0) {

System.out.println(i);i = i - 1;

}

Scanner in = new Scanner(System.in);

//keep asking the user for a nonnegative number until//they get it right!int j = -1;while(j < 0) {

System.out.println("Enter a nonnegative number");j = in.nextInt();

}System.out.println("You said: "+j);

//adding up 0 through 100int sum = 0;int counter = 0;while(counter <= 100) {

sum = sum + counter;counter = counter + 1;

}System.out.println("The sum of 0 + 1 + ... + 100 = " + sum + ", yeah!");

//an infinite loop (you usually don't want that!)boolean b = true;while(b) {

System.out.println("hi");}

// Be careful of = versus ==// = is used for assignment (means left side becomes the right side)// == is used for testing equality.

}}

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

int k = 3;int j = 0;

System.out.println(j % k); //remainder after dividing 7 by 3.//should be 1.

//The code block of this if statement always executes.if (true) {

j = 7;j = j + 1;

}

j = j / 2;

}}

11a)public class Javadocs {

public static void main(String[] args) {//Notes on using the Javadocs:

//When you see a method with "static" at the left, this//means you call it with the name of the class, a period, and//then the name of the method. For example:

//The javadoc says "static double random()", so you call it using:double r = Math.random();

//"static methods" are also sometimes called "functions".//They simply take input and produce output.

//This shows a combination of getting a static double from the Math class,//and using it in a static method (the cosine function).//The javadoc says "static double cos(double a)"double c = Math.cos(Math.PI);

//If there isn't a "static" labeling a method, that means the method is used on

//objects of that class. Objects are instances of a class.//For example, "hello" is an instance of the String class type.//The analogy is that 3.4 is an instance of the double primitive type.

//To use these methods, you use the name of the object// (or the variable containing it, more precisely),// a period, and then the name of the method.

//In either case (static or not), you have to supply whatever//inputs ("arguments") are required in between the parenthesis.

//using "static int max(int a, int b) " from the Math class.

System.out.println(Math.max(4,5));}

}

11b)import java.util.*;

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

Scanner myScan = new Scanner(System.in);

System.out.println("hello?");String t = myScan.nextLine();

if (t.equals("hello")) {System.out.println("hi");

}else {

System.out.println("eh?");}

//The == operator compares primitives to see//if they are the same value.

//But when it comes to objects, it compares//to see if they are the EXACT same object in memory.//Thus we have to use the equals method instead.

System.out.println("What state are you in (two letter abbreviation)?");String state = myScan.nextLine();

double tax;if (state.equals("MI")) {

tax = 6;

}else if (state.equals("WI")) {

tax = 5.5;}else if (state.equals("FL")) {

tax = 7 * Math.random(); //random tax between 0 and 7.}else {

System.out.println("I don't know that place called "+state);tax = 0;

}

System.out.println("The tax is "+tax+"%");

String a = "hello";String b = "zebra";

if (a.compareTo(b) < 0) {System.out.println(a +" comes before " + b);

}else if (a.compareTo(b) > 0) {

System.out.println(a +" comes after " + b);}else {

System.out.println(a +" must be equal to " + b);}

}}

12a)// The "Integer class" is different than the primitive int type.// Here I used the Integer class to convert a String to an int.

// http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Integer.html

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

//how to convert a String into an int.

String t = "3872";int i = Integer.parseInt(t);System.out.println(i);

i = Integer.parseInt("999");System.out.println(i);

}

}

12b)import java.util.*;

//A program where the user guesses the computer's secret number.public class Guess {

public static void main(String[] args) {//create a scannerScanner userInput = new Scanner(System.in);

//Generate and store a random number (1 - 100)int secret = (int)(Math.random() * 100) + 1;//the (int) is called a "cast" and it forces the//double value into an int value (truncating fractions)

int guess = -1; //user's guess//Loop as long as the guess is wrong:while(guess != secret) {

//prompt the user to make a guessSystem.out.println("Take a guess.");

//get the guessguess = userInput.nextInt();

//Compare to see if they got it right:if (secret == guess) {

//If they got it right, say so.System.out.println("You got it right.");

}else if (guess < secret) {

//If guess is too low, say so.System.out.println("You guessed too low.");

}else {

//If guess is too high, say so.System.out.println("You guessed too high.");

}}

//Tell user: Congrat's you're great.System.out.println("You won!");

}

}

16)import java.util.*;

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

Scanner userIn = new Scanner(System.in); //creates a Scanner object

System.out.println("Are you ages 4 and up?");String answer = userIn.nextLine();

if (answer.equals("no")) {System.out.println("You aren't old enough to play");System.exit(0); //Exits the program immediately.

}

int player1; //current position of player 1int player2; //current position of player 2player1 = 0; //start just before the first square (off the board)player2 = 0; //start just before the first square (off the board)

while(player1 < 100 && player2 < 100 ) { //keep looping as long as the game is in progress.

System.out.println("Player 1's turn. Hit <enter> to roll.");userIn.nextLine();int dieRoll = (int)(Math.random() * 6) + 1;if (player1 + dieRoll <= 100) {

player1 = player1 + dieRoll;

}System.out.println("You rolled a "+dieRoll

+" and landed on square "+player1);

//chutes and ladders part.if (player1 == 1) {

player1 = 38;System.out.println("Ladder to "+player1);

}else if (player1 == 4) {

player1 = 14;System.out.println("Ladder to "+player1);

}else if (player1 == 16) {

player1 = 6;System.out.println("Chute to "+player1);

}//TODO: missing a lot more chutes and ladders

if (player1 < 100) { //if player 1 hasn't won yet, p2 gets a turn.System.out.println("Player 2's turn. Hit <enter> to roll.");

userIn.nextLine();dieRoll = (int)(Math.random() * 6) + 1;if (player2 + dieRoll <= 100) {

player2 = player2 + dieRoll;}System.out.println("You rolled a "+dieRoll

+" and landed on square "+player2);

//chutes and ladders inif (player2 == 1) {

player2 = 38;System.out.println("Ladder to "+player2);

}else if (player2 == 4) {

player2 = 14;System.out.println("Ladder to "+player2);

}else if (player2 == 16) {

player2 = 6;System.out.println("Chute to "+player2);

}//TODO: missing a lot more chutes and ladders

}}

if (player1 == 100) {System.out.println("Player 1 wins");

}else if (player2 == 100) {

System.out.println("Player 2 wins");}

}

}