Week Three

Refresher Hello World Exercise.

Variables Introduction

• Refer w3schools

Data types

• Refer w3schools

public class WeekThreeExOne {
    public static void main(String args[]) {
        // variable_type variable_name = value;
        int year = 2022;                    // Integer (whole number)
        char gender = 'M';                  // Character
        boolean isPrimaryEmail = true;      // Boolean valid values are true or false
        String firstName = "Ram";           // String
    }
}

In Class Exercise

For our final project we will build a simple eCommerce App (Similar to amazon), Part of the project will involve registration. Assume we are going to collect the following information during registration.

• email
• primary email (Assume only valid values are true or false)
• first name
• last name
• middle initial (Assume this can only be a single letter)
• DOB Month
• DOB Day
• DOB Year

Create a program to print above registration details. As a part of the exercise you will practice.

• Syntax for declaring a variable.
• Choosing the correct data type.
• Initialize variables with values.
• Solving any compilation issues.
• Example - In the following example we created a variable called firstName of type String and assigned it a value Ram, As a part of the exercise add you will need to add remaining registration fields.

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

        String firstName = "Ram";

        System.out.println("First Name : "+firstName);
    }
}

Methods

• Refer w3schools, We will revisit methods in much more detail in the next couple of weeks.
• In general a method is a block of code that does something. For example length method in String class calculates the length of the string. A method normally has the following
  • name of method
  • return value and type
  • arguments/parameters
  • body/implementation - we will not worry about this for this class, we will revisit this next week.

String methods

• Example methods that return a value
  • length
  • toUpperCase
• Example methods that take an argument
  • substring

Example - Find length of first name String. (Note - string length method does not take any input arguments/parameters, returns a int value that is the length of the string)

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

        String firstName = "Ram_Bethina";

        System.out.println("First Name : "+firstName.length());

        
    }
}

In Class Exercise

• Convert values provided in First Name to Upper Case, ie if I declare String firstName = "Ram Bethina" output of my program should be First Name : RAM BETHINA, HINT - User toUpperCase() method.

Example - concatenate 2 strings. (Note - string concat takes an input argument and returns a contactenated string)

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

        String firstName = "Ram";

        System.out.println("First Name : "+firstName.concat(" Bethina"));

        
    }
}

In Class Exercise

• Assume String fullName = "abraham lincoln"; Write a program that prints out first 8 characters, HINT use substring method.

Assignment - Input cleanser

Normally user input data needs to be cleaned. As part of our program we are going to implement a simple input cleanser.

Assume that we do not want ‘_’ in first name and last name,

PART 1 - Write a program that replaces any occurence of underscore _ with a space ` `.

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

        String firstName = "Ram_Bethina";

        System.out.println("First Name : "+firstName.<HOME WORK, REPLACE WITH A FUNCTION IN THE STRING CLASS THAT REPLACES _ WITH EMPTY SPACE>);
    }
}

OUTPUT SHOULD BE

First Name : Ram Bethina

Hint - You may want to use the following method on String class.

• replaceAll - Look at API for additional details., But at a high level this takes 2 arguments. As an example replaceAll(" ", "_") will replace all occurences for space with underscore

PART 2 - (This may be a bit more challenging but I would like you to give it a try.) Write a program that capitalizes the first letter of first name. So if I declare my first name to be

String firstName = "ram bethina";

OUTPUT SHOULD BE

First Name : Ram bethina

Hint, you may want to use the following String API methods.

• substring
• toUpperCase
• concat

Assignment submission

• I would prefer if you send me a link to your project in github, If you dont have time to get git working you can slack me the assignment for this week.
• If you completed last weeks assignment you may have created a github account. If not create a github account.
• Please follow the link which talks thru IntelliJ integration with git and github.