Java5 TutorHomepage

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.


Learn Java5

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:


Beginning Java5

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.


Objects & Classes

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.


OO Concepts

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.


Flow Control

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.


API Contents

In our fifth section on learning Java5 we begin our investigations of the Java API by looking at the String, StringBuilder and 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 java.lang 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.


Concurrency

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.


Collections/Generics

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 java.util.Arrays and java.util.Collections 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 Comparable and Comparator interfaces.


Java5 Certification

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.


1: Declarations, Initialization and Scoping

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.


2: Flow Control

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 and 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.


3: API Contents

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 BufferedReader, BufferedWriter, File, FileReader, FileWriter and 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.


4: Concurrency

This section is all about concurrency and we start it by looking at thread definition, instantiation and execution using the java.lang.Thread and 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.


5: OO Concepts

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.


6: Collections/Generics

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 equals() and 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 java.util.Comparator and java.lang.Comparable interfaces for sorting collections and the effect of natural ordering of primitive wrapper classes and java.lang.String on sorting.


7: Fundamentals

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 the 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.



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