Before you do this section, watch the videos here: https://www.dropbox.com/sh/v0xcqgjkia6brmm/AABRKcrZjwhkR1j14NsMcd4za?dl=0

Older programming languages distinguish between Functions and Procedures. Very simply, a function returns a value, a procedure does not.

Java rolls both of these into one concept: Methods. A method always has a return type. If the return type is void it is what an older language would call a procedure, otherwise it’s a function.

Here is an example method:

public void spoons (String s, int i)

Two example Classes

public class Main {

    public static void main(String[] args)
    {
	Person p1 = new Person("Bloggs", "Joe");
	p1.setSex("M");

	Person p2 = new Person("Baker", "Jill");
	p2.setGender("F");

	p1.printPerson();
	p2.printPerson();
    }

}


public class Person {

     private String surname;
     private String forename;
     private String gender;     

    Person(String surname, String forename)
    {
	this.surname = surname;
	this.forename = forename;
    }

    public void setGender(String s)
    {
	if(!(s.equals("F")|s.equals("M")))
	{
	    System.out.println("Validation error!");
	} else
	{
	    sex = s;
	}
    }

    public void printPerson()
    {
	System.out.println(surname + " " + forename + " " + gender);
    }

}

Method Exercise: Progress Tracker

Write a class Pupil that will track pupils’ progress through a year. The class will store pupils’ grades as percentages.

1. Add private member variables String forename, surname
2. Add private member variables int target, autumn, spring, summer
3. Add a constructor method that will accept the parameters forename, surname, target
4. Test the constructor by adding the following pupils: Joe, Bloggs, 70 and Jill, Cooper, 75
5. Add accessor methods to setAutumn(), setSpring(), setSummer()
6. Add accessor methods to getAutumn(), getSpring(), getSummer()
7. Add the following grades to Joe Bloggs:  Autumn 55, Spring 65, Summer 75
8. Add the following grades to JIll Cooper:  Autumn 50, Spring 60, Summer 70
9. Add a method average() to return a double showing the average percentage a pupil has. Print out Joe and Jill’s average scores
10. Add a method progress() that will return a String saying whether the pupil is above target, on target or below target on the summer test.
11. Check this method works on Joe and Jill
12. Add a print() method that will print out the pupil’s details in a suitable format

Extension Work

• Add a validation() method to check that grades entered lie between 1 and 100
• Modify your average() method so it will return a correct average if only one or two grades have been entered so far
• Add a static int variable aBound to record the grade A boundary.
• Add the appropriate setters and getters to aBound
• Set up a Pupil [] array in your Main class to handle your pupils
• Add a save() method to your Pupil class that will write the pupil data to file

Iterate Through an Array

String [] day =    {"Monday", "Tuesday", "Wednesday", 
		    "Thursday", "Friday", "Saturday", "Sunday"}; 

for(int i = 0; i<day.length;i++)
{
    System.out.println(day[i]);
}

Random Element of Array

String [] day = {"Monday","Tuesday","Wednesday","Thursday",
"Friday","Saturday","Sunday"};
int d = (int)(Math.random()*7);
System.out.println(day[d]);

Splitting a String into Words

String s = "This is an example string";
String [] seperated = s.split("\\s+");
for (int i=0; i<seperated.length; i++)
{
	System.out.println(seperated[i]);
}

for each loops

String [] day =    {"Monday", "Tuesday", "Wednesday", 
		    "Thursday", "Friday", "Saturday", "Sunday"}; 

for(String s: day)
{
    System.out.println(s);
}

Exercise

1. int [] numbers = {3,5,3,4,7,8}; Print out the second element of the array
2. Make a String array of the months of the year. Print out all the months.
3. Print out a random month of the year
4. Create an int array recording the number of days in each month
5. Print out all the months and the days in each month.
6. int [] numbers = {3,5,5,4,8,8,10,2}; Print out the total of all the numbers in the array. Print out the average
7. Make a string array with the words “First”; “Second”; “Third”; … “Twelfth”. Write a for loop to print out “On the First Day of Christmas,” “On the Second Day of Christmas” etc.
8. Separate the following string using the “,” as a token. Print out all the elements. String s = “1,5,6,1,7,1,4,3,1,4,5,6,1,5,3,5,6,4,4,8”;

Extension

Paste the following code into your IDE, and then do the questions below.

String [] question = { "What is the capital of France?",
		       "What is the capital of Germany?",
		       "What is the capital of Spain?"};
String [] answer = {"Paris", "Berlin","Madrid"};

int score = 0;
Scanner scan = new Scanner(System.in);
String input;

for(int i= 0; i<3; i++)
{
     System.out.println(question[i]);
     input = scan.nextLine();
     if(input.equals(answer[i]))
     {
	 score++;
     }
}

System.out.println("You scored "+ score + " out of "+ question.length);

1. Run the code to check it works
2. Add some extra questions and answers. Check the code still works
3. Add code to print out the correct answer if the user gets a question wrong
4. Alter your code so that questions and answers are read in from text files

Counting Down

int count = 10;
while (count>0)
{
    System.out.println(count);
    count = count - 1;
}
System.out.println("Lift off!");

Counting Objects

String colours = "red blue red blue blue blue blue red blue red blue "
		 + "red blue blue red blue blue blue red blue red red "
		 + "blue blue red red red red blue red blue red blue blue";


Scanner scan = new Scanner(colours);
int redcount = 0;

while (scan.hasNext()) {
    String s = scan.next();
    if (s.equals("red")) {
	redcount = redcount + 1;
    }
}
System.out.println("Number of reds " + redcount);

A Basic Question Loop

Scanner scan = new Scanner(System.in);
String answer;

do
{
    System.out.println("What's the capital of France?");
    answer = scan.nextLine(); 

}while (!answer.equals("Paris"));
 System.out.println("Correct!");

A Question Loop with a Count

Scanner scan = new Scanner(System.in);
String answer;
int count = 0;

do
{
    System.out.println("What's the capital of France?");
    answer = scan.nextLine();
    count = count + 1;

}while (!answer.equals("Paris"));
 System.out.println("Correct!");
 System.out.println("It took you " + count + " guesses");

A Question Loop with a Flag

Scanner scan = new Scanner(System.in);
int answer;
boolean isNotDone = true;

do
{
    System.out.println("Enter an Integer, 0 to end.");
    answer = scan.nextInt();
    System.out.println(answer + " squared = " + answer * answer);
    if (answer == 0)
    {
	isNotDone = false;
    }

}while (isNotDone);
 System.out.println("Done!");

A Question Loop with a Count and a Flag

Scanner scan = new Scanner(System.in);
String answer;
boolean isCorrect = false;
int count = 0;
do
{
    System.out.println("Enter the password");
    answer = scan.nextLine();
    if (answer.equals("Java"))
    {
	isCorrect = true;
    }
    count = count + 1;
 }while(!isCorrect & count <3 );


if (isCorrect)
{
    System.out.println("Correct password");
}
else
{
    System.out.println("Incorrect password");

Exercise

while Questions

1. Use a while loop to print out the integers from 1 to 10
2. Use a while loop to print out the even numbers from 2 to 20
3. Use a while loop to print out the four times table
4. Use a while loop to print out the five times table in the form “n x 5 = 5n”
5. Use a while loop to print out the sequence 7,10,13,16,19,22,25
6. Use a while loop to print out the sequence -0.3, -0.2, -0.1, 0, 0.1, 0.2
7. Use a while loop to print out the sequence 64, 32, 16, 8, 4, 2, 1
8. Use a while loop and Scanner to count how many heads and tails there are in the String below. (nb. you should carefully copy and paste the String into your program)

String coins = “head head tail head tail head head head tail head tail head tail head head head tail “+ “head tail head tail head tail head tail head tail tail tail head head head tail “+ “tail head tail head tail tail head head head tail tail tail head tail head head head tail “+ “head tail tail head tail head head head tail head tail head tail head head head head “+ “head tail head tail head tail head head head tail tail head tail head tail head head head head”;

1. Write a code to find the number of times the word “never” appears in the following poem: I never saw a purple cow, I never hope to see one, but I can tell you anyhow, I’d rather see than be one.”
2. Now search the Internet for the text to the poem “McCavity the Mystery Cat” Write code to count the number of times the word McCavity appears.

do while Questions

1. Make the computer keep asking “Are we there yet?” until the answer yes is input.
2. Ask the user the to guess a number between one and ten. Hard code the number 4 as an answer. The computer will print out how many guesses the user takes before they get the correct answer.
3. Modify program 2 so that the computer chooses a random number as the answer.
4. Write a higher lower game. Modify program 3. The computer thinks of a number between 1 and 100. The user tries to guess the number, and the computer tells the user if their answer is higher or lower. Whe then user guesses correctly, the computer congratulates the user and tells them how many guesses it took them.
5. Wrtie a password checker. The user cannot proceed until they enter the correct password.
6. Modify your password checker so that the user sees the message “Locked Out” if they fail to guess the password in three guesses.

Extension

The skeleton code below is intended to guess the number the end user is thinking of. The end user can enter yes if the computer guesses the answer, higher if the number is higher and lower otherwise. Copy the code into the IDE and complete it.

Scanner scan = new Scanner(System.in);
double num = Math.random()*100;
int ran = (int)num+1;
int guess = 50;
int high =100;
int low= 0;
String input = "";
boolean isCorrect = false;

do
{
    System.out.println("Is the number " + guess + "?");
    input = scan.nextLine();
    if(input.equals("yes"))
    {
	isCorrect = true;
    }
    else if(input.equals("higher") )
    {
	low = guess;
	guess = low + (int)(high-low)/2;
    }


}while(!isCorrect);

Print the numbers 1 to 9

(look very carefully at the semi colons below!)

for(int i= 1; i<10; i=i+1) {
    System.out.println(i);
}

Print the numbers 1 to 10

for(int i= 1; i<=10; i=i+1) {
    System.out.println(i);
}

Print the numbers 10 to 1

for(int i= 10 ; i>0; i=i-1) {
    System.out.println(i);
}

Prints the first ten squared numbers in the form “3 squared = 9”

for(int i =1; i<=10; i =i+1) {
    System.out.println(i+ " squared = "+ i*i);
}

Nested for loops

The following nested for loops print out the pattern triangle pattern below. Note the j<i condition in the second for loop and the use of print() and println().

for(int i = 0; i < 6; i++) {
	   for(int j = 0; j < i; j++) {
	       System.out.print("*");
	   }
	   System.out.println("");
}

*
**
***
****
*****

Exercise

Use for loops to print out the following:

1. Numbers from 1 to 70 inclusive
2. Numbers from 10 to -10 inclusive
3. Odd numbers from 1 to 19 inclusive
4. Even numbers from 10 to -20 inclusive
5. The sequence 0.3, 0.4, 0.5, 0.6, 0.7
6. The sequence 0.1, 0, -0.1, -0.2, -0.3
7. The square numbers 1, 4, 9, 16, … 81, 100
8. Five random integers between 1 and 10 inclusive
9. All multiples of 3 up to 99
10. The powers of 2 up to 2⁸ (2, 4, 8, … 128, 256)

Nesting Loops

Use nested for loops to print out the following patterns

*
**
***
****
*****
******
*******
********
*********

*****
****
***
**
*

**
****
******
********

1. 6!, pronounced 6 factorial, means 6x5x4x3x2x1. Write a program to print out the first 10 factorial numbers.
2. Print out the times tables for 1 to 10. Print them out in the format “2 x 3 = 6”
3. Print out a chess board grid using 1s and 0s e.g. 0 1 0 1 0 1 0 1, then 1 0 1 0 1 etc to make an 8×8 grid.

Extension

Print out the following patterns, either using nested for loops or some other way…

     *
    **
   ***
  ****
 *****
******

   *
  ***
 *****
*******

   *
  ***
 *****
*******
 *****
  ***
   *