Section Overview In this section, we’re going to talk about how do we write code to handle situations. That where things might not go as according to plan. Give you an example. You’re running a program. It connects to the database, but the database is down. How do you prepare for that in your code? Well, Java gives us something called exception handling. And that’s the concept we’re going to learn in this section. Throwable Whenever we write a program, we really hope that everything is going to go according…

Section Overview In this section, we’re going to look at another new API that was added to Java Eight. It’s called the Java Time Library and it’s going to give us classes to work with what it sounds like time, time and date. So we’ll look at local date, local date time, local time, and another class called period. So let’s start working with dates. LocalDate Java Eight gave us a brand new set of classes to work with for dealing with dates and times and durations. And they replaced…

Sets The next type of collection we’re going to look at is the set. And a set is another subtype of the collection interface. Now, the characteristics of a set is that no duplicate objects are allowed and so it’s going to use the equals method to determine whether or not an object is duplicate. Once again, another reason why you want to override equals. Generally speaking, the orders of the elements in a set are not maintained, although there is something called a tree set which will allow you…

Section Overview We’ve talked about the array and we saw that it’s a great way of creating collections of related objects together. But we saw that there were some limitations as well. So we’re going to look at something that’s a little bit more flexible. It’s called a collection. And so we’ll start right away talking about array lists and so on. Let’s start with lecture number one. When Arrays Are Not Enough When we code, we very frequently have to put together collections of things. We’ve seen that we…

Multi-Dimensional Arrays So far we’ve been looking at singledimensional arrays and that’s predominantly what you’re going to be using. Java does, however, support multidimensional arrays. The way that we create this is that each dimension will have its own set of square brackets. So here’s an example of creating a twodimensional array. Notice that we’ve got two sets of square brackets on the left side as well as two sets on the right. What we’re saying is this is a two dimensional array. Now the way that multi dimensional arrays…

Section Overview In this section, we’re going to begin our discussion about different kinds of collections. And we’re going to look at one of the most basic forms of collection, which is called an Array. So an Array is just a way for us to take a bunch of related things, put them all together and store them in memory, volatile memory. That is, memory that could be erased if the program shuts down. But while we’re working with our program, we’re going to need to access data. And this…

Interfaces: Part 2 We create these interfaces and then these interfaces in turn are implemented by classes. So just like an abstract class, you can never create an instance of an interface. You can never just say new interface. That’s not legal. In Java, there is a concept called an anonymous class which we don’t cover in this course. And the syntax makes it look like you’re creating a new interface. But you’re never just of saying new interface. And what the interface is doing is it’s setting up a…

Section Overview This is the final section in which we are going to be talking about the pillars of objectoriented programming, and this one is based on abstraction. Specifically, we’re going to look at abstract classes and interfaces to see how we can create a consistency among our program. And also, again, like polymorphism, introduce substitutability and flexibility into our apps. So let’s hit that first lecture. Abstract Classes: Part 1 We’ve talked about several different pillars of objectoriented programming. We’ve seen encapsulation, inheritance, polymorphism, and now we’re going to…

UNION – COMBINING ROWS FROM TWO QUERIES WITHOUT DUPLICATES Using Set operators, we can combine the results of multiple queries into a single result set. For example, select Call one from Tab One will give this result. Select call three from tab two will give this result. Now I can combine both into a single result set by using Set operations. Union is one of the Set operators. Let us explore it. Now, if I do, select call one from tab one. Union select. Call three from tab two. Then…

SUBQUERIES – DEFINITION AND SUBQUERY IN THE SELECT CLAUSE Sub queries. Let us assume that I want to see today’s Date, the number of employees I have and how much salary I pay. I can do all this by running three queries separately select Sys Date from Dual gives me today’s Date select Count Star from Employees gives me the total number of employees I have and Select Some Salary from Employees gives me the total salary that I am paying. But these are three separate queries with separate results….