Semester | Collection of small apps and libraries

how can I satisfy all the conditions here? can't find any example online. I just don't know what code to use. I tried doing some coding but I know it was way off to what was actually ask to me. The problem was

"Write a java class called Student. The Student class will have four data members: name (astring), age (an int), semesterNo (an int), and GPA (a float). Write a java program to test your Student class. Your program should: Create three Student objects, enter their name, age, semesterNo (assuming a value from 1 to 8), and GPA(assuming value from 0.0 to 4.0) and display the data for each Student. Continuing the Student class, calculate and display the average GPA of the three Students.(user input required)"

and the code I come up was `

I created this DB:

I am asked to find the teacher's name and titles of all the courses they have taught at least twice.

My database:

I've finished my first semester in a college-level SQL course where we used "SQL queries for Mere Mortals" 3rd edition.

Long term I want to work in data governance or as a data scientist, so digging deeper is needed and I found the Stanford SQL course. Today taking the first mini quiz, I got the answers right but on these two I'm not understanding WHY I got the answers right.

My 'SQL for Mere Mortals' book doesn't even cover hash or tree-based indexes so I've been searching online for them.

I mostly guessed based on what she said but it feels more like luck than "I solidly understand why". So I've ordered "Introduction to Algorithms" 3rd edition by Thomas Cormen and it arrived last week but it will take me a while to read through all 1,229 pages.

Found that book in this other stackoverflow link =>https://stackoverflow.com/questions/66515417/why-is-hash-function-fast

Stanford Course => https://www.edx.org/course/databases-5-sql

I thought a hash index on College.enrollment would not speed up because they limit it to less than a number vs an actual number ?? I'm guessing per this link Better to use "less than equal" or "in" in sql query that the query would be faster if we used "<=" rather than "<" ?

This one was just a process of elimination as it mentions the first item after the WHERE clause, but then was confusing as it mentions the last part of Apply.cName = College.cName.

My questions:

1. I'm guessing that similar to algebra having numerators and denominators, quotients, and many other terms that specifically describe part of an equation using technical terms. How would you use technical terms to describe why these answers are correct.

2. On the second question, why is the first part of the second line referenced and the last part of the same line referenced as the answers. Why didn't they pick the first part of each of the last part of each?

For context, most of my SQL queries are written for PostgreSQL now within PyCharm on python but I do a lot of practice using the PgAgmin4 or MySqlWorkbench desktop platforms.

I welcome any recommendations you have on paper books or pdf's that have step-by-step tutorials as many, many websites have holes or reference technical details that are confusing.

Thanks

In this University Database:

We have a dictionary file that contains words. We need to read this file and print words that are only made up of characters that exist in a particular set { 'm', 'o', 'n', 'k', 'e', 'y' }. (These have words have a fixed length. So if length = 2, then word can be 'no', 'on', etc.)

I am making an attendance app on android studio, but whenever I try to log in using correct credentials I need to click twice on the login button to move forward to the next activity. I tried Asynctasks because of its background thread, after the same result I just reverted back

So, at first click nothing happens but as soon as please wait dialog box disappears and if I click like in under a second or two then it moves to the next activity.

clicking on login fetches some data from the server after the server has validated that the login exists and is correct. when data is received then the new activity is supposed to start since that received data will be shown in the next activity. (i have a list that is checked if it has data then it moves forward)

Login Activity code:

I have this pipeline that handles data like this

how to insert select option value in database using checkbox?When I click checkbox and click enroll button ,select option doesn't inserting selected value.I have 3 options(Regular,Retake,Recourse) in "examtype" table but when I choose more than one subject select option not working perfectly. Here is my code... here is my select option image