The aim of this site is to learn and improve knowledge of the Java programming language, version 5 and give an insight into the Java Standard Edition 5 Programmer Certified Professional Exam (IZO-583), which when passed gives the Oracle Certified Professional, Java SE 5 Programmer certification. The site is divided into two sections covering the Java5 programming language and the certification.
This part of the site covers the Java language from the ground up, introducing different aspects of the language as we work through the sections detailed below:
We start out by downloading a JDK and setting up our environment before beginning our journey into Java5. With the environment set up we introduce the code structure of a Java source file and look at syntax. After this we look at the primitive variables available in Java before discussing method scope. We then take an in-depth look at the symbols used for mathematical and logical manipulation that are recognized by the compiler and commonly known as operators. Every computer language has conditional branching and loop structures and Java is no exception. We finish off this section with a look at the conditional and loop statements available in Java5.
The main emphasis of the Beginning Java5 section of the site was an introduction to the basic building blocks required to write a Java program. This section is all about objects
and the classes used to construct them. We start by looking at a predefined data type, the
Array object. Investigation of this class will give us an insight into using objects and classes before we
start to create our own. After this we examine class structure and the syntax required for class construction, before investigating reference variables and how to use them in Java. We have used methods throughout the lessons
so far, and the next lesson in the section goes into these members in much more detail. We then look at instance variables and their scope before studying constructors which are used to instantiate our objects. We finish the
section by taking an in-depth look at static members, followed by a new feature in Java5, enumerations.
Up until now, for learning purposes, we have ignored many important object oriented concepts that we can use within our Java programs. This neglect is rectified in this section where we start our study of OO concepts by
looking at encapsulation and how to protect our data. We then tackle inheritance over two lessons where we look at creating hierarchies, overriding methods and the use of
super. After this we look at
abstraction and how we apply it to our classes and methods. We then examine polymorphism and how to use it with our methods, arguments and return types. Our investigation of polymorphism continues as we investigate interfaces
and their usage. We then return to the idea of encapsulation as we look into nested classes, what they are and how to use them. We finish the section with a detailed look at the
Object class and the methods
we inherit and can override in our subclasses.
In this section we finish our studies on flow control by studying exceptions and assertions. Firstly we look at Java exceptions where we make a thorough investigation of the exception hierarchy and how Java's exception architecture hangs together. With an overview of exceptions under our belt we look at handling the various forms of exception in our code. After this we look at declaring and throwing exceptions in our code, which we can deal with straight away or allow to propagate up the stack to be dealt with elsewhere. We finish of our investigation of exceptions by creating our own bespoke checked and unchecked exceptions for when needed. With exceptions covered we turn our attention to the assertion mechanism available in Java. We learn appropriate uses of assertions and when not to use them. We also look at the runtime commands used to enable assertions, as and when required.
In our fifth section on learning Java5 we begin our investigations of the Java API by looking at the
StringBuffer classes. These predefined classes come
with a multitude of methods for working with strings and are part of the
java.lang package which is implicitly imported into all our Java programs for us. After this we broaden our horizon of Java
by investigating classes that are not implicitly imported into our programs. Before we look at other parts of the Java API however, we need to take a closer look at how Java stores predefined classes into namespaces,
which Java calls packages, and how we can import these packages into our programs. With knowledge of packages under our belt we can now look at parts of the Java API outside the default
package. Our first port of call is how we use I/O in Java and for this we will look at the
java.IO package. We start our exploration of Java I/O by looking at the class hierarchies involved
and then take an in-depth look at the byte stream classes and character stream classes used for this purpose. After this we look at the classes available for working with dates, numbers and
currencies. Most languages have an implementation of regular expressions and Java is no exception and we look at the classes used for pattern matching. We finish off our tour of the Java API
by looking at formatting and tokenizing our data.
In our sixth section on learning Java5 we look at multithreading and how to run parts of our program concurrently. We explain the terminology behind concurrency before looking in detail at running parts of
a program concurrently by subclassing the
Thread class and also by declaring a class that implements the
Runnable interface. Running separate threads
at the same time is great and we can certainly improve the performance of our programs using multithreading. But what happens when concurrent threads need to access and update some shared resource?
Java deals with this problem with synchronization and we investigate how we can control access to our code by synchronising at the method or block level. After this we investigate thread priorities and how
we can have the priority set automatically by the invoking thread or assign thread priorities ourselves using methods of the
Thread class. We finish our look at concurrency by
looking at how threads can interact with each other when they are within a synchronized method or code block.
In our final section on learning Java5 we look at collections and investigate generics. We start by defining what a collection is and look at some diagrams of the collection types to get a feel for the various
structures of the classes and interfaces involved. After this we make an in-depth investigation of generics and unravel the strange syntax we get with it. Following on from this we examine the various hierarchies
within The Collections Framework by taking a look at some concrete implementations of Sets, Lists, Maps and Queues. We than look at the
classes that contain a lot of
static utility methods we can use with our collections. We finish the section by finding out how to sort our collections using the
This section of the site covers the requirements for the Java Standard Edition 5 Programmer Certified Professional Exam (IZO-583) which when passed gives the Oracle Certified Professional, Java SE 5 Programmer certification.
In this section we look at all types of class declaration and extension and how to use interfaces and the package and import statements. We examine the declaration, initialization and usage of primitives, arrays, enums, and objects as static, instance, local variables and their respective scopes. After this we cover correct use of overriding and overloading of methods as well as identifying legal return values for methods. we investigate constructors to determine if a default constructor will be created, and if so, determine the behaviour of that constructor. We finish of this section by studying class instantiation and how to instantiate nested and non-nested classes.
In this section we look at the different syntax we can use to affect the flow of logic through our programs. We start by looking at code to implement if
switch statements whilst identifying legal argument types for them. We then investigate the different types of loops available in
Java and the iterators and their usage within a loop. We will also look at how we can break from a loop, continue from within a loop and label a loop to continue execution from. We continue our study of flow
control by looking at assertions and when, and when not, they should be used. We finish our certification lessons on flow control by looking at exceptions, handling exceptions and how to declare methods and
overriding methods that throw exceptions. We also need to understand what happens to our code when an error or any type of exception occurs in a code fragment and what happens when particular exceptions occur.
We start this section by looking at code that uses the primitive wrapper classes and/or autoboxing and unboxing. We then look at the differences between the String, StringBuilder, and StringBuffer classes. After this
we investigate how we can use classes with the
java.io package to read from files, write to files and use the
PrintWriter sometimes in unison to create a software solution. We then use classes from the
java.text package to correctly format or parse dates, numbers, and
currency values for a specific locale including usage of the appropriate methods to use the default locale or a specific locale. We finish the section by looking at regular expressions and examine how to format and tokenize our data using Java5.
This section is all about concurrency and we start it by looking at thread definition, instantiation and execution using the
java.lang.Runnable classes. After this we investigate the different
states in which a thread can exist, and identify ways in which a thread can transition from one state to another. We finish the section by examining Java's locking mechanisms at the class and object level and
how we can synchronize methods and blocks of code to protect static or instance variables from concurrent access problems.
We start this section by looking at encapsulation, its advantages and how to achieve it within our code. We then look at the design principles of coupling and cohesion and describe the benefits of loose coupling and high cohesion. We then explain polymorphism and how we use it in the Java language before looking at object reference casting and determine when casting will be necessary whilst recognizing compiler vs. runtime errors, related to it. After this we examine the effect of modifiers on inheritance with respect to constructors, instance or static variables, and instance or static methods. We then look at code that declares and/or invokes overridden or overloaded methods and code that declares and/or invokes superclass or overloaded constructors. We finish the section by investigating code that implements "is-a" and/or "has-a" relationships.
We start this section by looking at the various types of collections and their corresponding interfaces and which type of collection is suitable for specific types of data. We then look at usage of
the Comparable interface. After this we look at the
equals() method of the
Object class which only ever returns
true when the reference variables refer to the same object which
isn't helpful when we want our collections sorted and stored dependent upon fields in the collection. So in this lesson we look at correct and incorrect overrides of corresponding
hashCode() methods and explain the difference between
== and the
equals() method. Generics were introduced with Java5 and in this lesson we look at the reasons for doing
this. We then look at usage of type parameters in class/interface declarations, instance variables, method arguments, and return types. We finish the lesson by looking at generic methods as well as methods that
make use of wildcard types. We finish the section by looking at array and list manipulation using the
java.util package, usage of the
interfaces for sorting collections and the effect of natural ordering of primitive wrapper classes and
java.lang.String on sorting.
In our first lesson within this section we look at access modifiers and also investigate the package and import statements. We then look at the
javac command we use to compile our Java programs and
java command to run our programs. We finish the lesson with a look at JAR files and how to use them. After this we look at method parameters that are passed into methods as reference variables
and primitive variables and the effects that modification within the methods has on the variable type in question. We then examine the point at which an object becomes eligible for garbage collection, and determine
what is and is not guaranteed by the garbage collection system and how the behaviors of
System.gc and finalization impact this. In our final lesson within this section we look at the various operators that are
available in Java and how to use them.