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Understanding the principles of Java


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Java Essential Training

with David Gassner

Video: Understanding the principles of Java

The Java programming language has been developed over the years following some very strict principles. The five principles of Java as declared when Java was created include, first, that it's a simple, object- oriented, and familiar language. Its simplicity lies greatly in its consistency. Once you learn how to do one thing in Java, you know how to do it the same way throughout the language because it never deviates from the way the language is architected. It's an object-oriented language. So once you understand the principles of encapsulation, inheritance, and polymorphism and how those are implemented in the Java programming language, you'll have a much better sense of how to architect your applications. And for developers who've worked with C-Style languages like C and C++, the syntax of Java is very familiar. Java was created to be robust and secure. Its robustness lies greatly in its object-oriented characteristics, because you're designing everything as an object, everything has methods or functions and properties also known as fields. And you create applications by combining multiple classes together. This lets you create your code in small chunks and it makes it easy to debug and maintain your applications over time. Java was designed to be portable, so that you'd be able to compile it once and then run your application on multiple operating systems and processors. Java was created to be high-performance. The original version of the Java Virtual Machine wasn't as fast as C++ applications, but over the years it's been improved enormously, and today Java applications run just as fast or sometimes even faster than applications built in C++. And finally Java was created as an interpreted language, it supports multithreading and it's dynamic. Interpreted, means that the application is compiled to a format that's interpreted at runtime rather than being run as machine code directly, this is what makes the applications portable. It's multithreaded, and it makes it easy to build applications that do more than one thing at the same time. And it's dynamic, in that it can change data types at runtime as long as those data types are compatible with each other. Here is the runtime architecture of Java. Again, it's an interpreted language, the application is compiled to bytecode rather than machine language, and that's what makes it portable between operating systems. Here is the software stat that's used at runtime when you run your application. You start with the operating system. You can run Java applications on Windows, Mac, Linux, Solaris, and any other operating system for which there is a usable Java Virtual Machine. The Java Virtual Machine you use most of the time will be the one provided by Oracle, the one that was created by Sun Microsystems, but there are other JVMs out there provided by IBM, the Virtual Machine that's provided for Android by Google and many others. On top of the Virtual Machine you add the core runtime and additional libraries. The core runtime is sometimes called the Java Class Library, and it consists of all of the functionality that's provided with the core Java developer toolkit. And finally your application runs on top of all that once again as compiled bytecode. So let's compare Java to a couple of popular languages. First C++, Java was originally created by C++ developers and they had in mind improving the developers' lot. Here are some ways in which Java is different from C++. If you're a C developer all of your code can be run in C++ as well. The two languages are compatible with each other, that's not true for Java. Even though Java has syntax that's very similar to C and C++, its code is unique. It has its own rules and its own syntax. I have mentioned earlier that C++ is compiled to native machine language and while that makes it very fast and gives it access to low-level functions, it means that your application has to be recompiled for each operating system and processor that you want to target. Java is compiled to bytecode. Because C++ is compiled to native machine language, it allows direct calls to the native system. In Java there is an interface called Java Native Interface sometimes called JNI, that lets you call those native functions through the JVM. C++ lets you write once and then as long as you followed standard C++ syntax you can recompile for each operating system you are targeting, whereas the principles of Java say that you can write once and run anywhere. Java runs in a protected virtual machine environment, and again, you have to go through that JNI interface to make those low-level system function calls. Here's a way in which the two languages are very different. C++ requires explicit memory management and uses pointers. C++ applications as a result can have memory leaks and it's up to the developer to make sure that they've sealed up all the holes in their application. In Java, memory is managed for you. When you create instances of classes or objects, the Java Virtual Machine automatically allocates the memory. And when you're done with the objects the JVM sweeps up the memory by destroying dereferenced objects, this is called the Garbage Collector. This means that in Java applications you don't have to know specifically how much memory is being used at any given time, you still have to pay attention to making sure that you only create the objects you need. And in C++ you can use multiple inheritance, this means that when you define an object you can inherit functionality for multiple super classes. The Java inheritance model is single inheritance so you can only inherit directly from a single superclass. This makes it easier to figure out where there are problems when your application has bugs. Let's also compare Java to JavaScript. Even though the names of these languages share the term Java, they are really not closely related. Java again wasn't compatible with previous languages even though it borrowed syntax from C. Java has morphed into a standard known as ECMA script or ECMAScript. Other languages that are based on the ECMAScript standard include Adobe's ActionScript 3.0 and JScript from Microsoft and a number of others. Java is compiled to bytecode and interpreted at runtime. JavaScript is interpreted directly from source code. Java can make native function calls through the JNI interface, while in JavaScript at least as it's implemented in a browser, is restricted to something called a browser Sandbox. It can only play in the Sandbox, and it can't make native function calls. Java is write once, run anywhere. JavaScript is even more portable in the sense that it has brought compatibility in many browsers and many operating systems. Java runs in a protected virtual machine but you have to explicitly have that virtual machine installed. And in a similar fashion JavaScript is executed by the browser and restricted to that browser sandbox for security. Both languages manage the memory for you, neither requires that you specifically allocate or deallocate memory. And in terms of inheritance, Java uses a traditional class-based inheritance where you define classes and then inherit their functionality. JavaScript uses something called prototype-based inheritance. This model allows you to add functions, properties, and other functionality to a pre-defined class at runtime, something Java doesn't allow you to do. So that's a look at the principles of Java and how you might compare this language to C++ and JavaScript. In the continuum of languages you might play C++ at the strictest level, Java somewhere in the middle, and JavaScript at the most dynamic. And you typically use Java when you want to build applications that rely on that language.
Expand all | Collapse all
  1. 10m 8s
    1. Welcome
      1m 3s
    2. Is this course for you?
      5m 35s
    3. Using the exercise files
      3m 30s
  2. 31m 24s
    1. The history of Java
      5m 19s
    2. Java compilation and syntax
      8m 54s
    3. Understanding the principles of Java
      8m 28s
    4. Choosing a development environment
      8m 43s
  3. 19m 5s
    1. Installing Java on Windows
      6m 42s
    2. Installing Eclipse on Windows
      3m 19s
    3. Exploring Java on Mac OS X Leopard and Snow Leopard
      2m 27s
    4. Installing Java on Mac OS X Lion
      3m 27s
    5. Installing Eclipse on Mac OS X
      3m 10s
  4. 46m 10s
    1. Creating a Hello World application
      11m 7s
    2. Exploring the Eclipse IDE
      8m 55s
    3. Compiling and running from the command line
      8m 2s
    4. Passing arguments to the application
      8m 17s
    5. Using the Java API documentation
      4m 5s
    6. Memory management and garbage collection
      5m 44s
  5. 58m 57s
    1. Everything is an object
      5m 59s
    2. Declaring and initializing variables
      9m 15s
    3. Working with numbers
      8m 32s
    4. Converting numeric values
      6m 40s
    5. Understanding operators
      7m 58s
    6. Working with character values
      5m 14s
    7. Working with boolean values
      5m 13s
    8. Outputting primitive values as strings
      5m 33s
    9. Creating a simple calculator application
      4m 33s
  6. 53m 40s
    1. Writing conditional code
      5m 35s
    2. Using the switch statement
      8m 50s
    3. Repeating code blocks with loops
      7m 35s
    4. Creating reusable code with methods
      6m 31s
    5. Declaring methods with arguments
      5m 41s
    6. Overloading method names with different signatures
      5m 53s
    7. Passing arguments by reference or by value
      5m 35s
    8. Creating a more complex calculator application
      8m 0s
  7. 20m 30s
    1. Using the String class
      5m 44s
    2. Building strings with StringBuilder
      3m 34s
    3. Parsing string values
      3m 19s
    4. Working with date values
      7m 53s
  8. 20m 44s
    1. Understanding compile-time vs. runtime errors
      4m 5s
    2. Handling exceptions with try/catch
      4m 55s
    3. Throwing exceptions in methods
      2m 50s
    4. Using the debugger
      8m 54s
  9. 32m 22s
    1. Using simple arrays
      4m 47s
    2. Using two-dimensional arrays
      6m 17s
    3. Managing resizable arrays with ArrayList
      7m 14s
    4. Managing unordered data with HashMap
      6m 5s
    5. Looping through collections with iterators
      7m 59s
  10. 52m 2s
    1. Understanding encapsulation
      5m 59s
    2. Creating and instantiating custom classes
      8m 8s
    3. Organizing classes with packages
      6m 47s
    4. Creating and using instance methods
      6m 52s
    5. Storing data in instance variables
      6m 56s
    6. Using constructor methods
      5m 40s
    7. Managing instance data with getter and setter methods
      8m 26s
    8. Using class variables and Enum classes
      3m 14s
  11. 41m 15s
    1. Understanding inheritance and polymorphism
      9m 12s
    2. Extending custom classes
      9m 1s
    3. Overriding superclass methods
      3m 8s
    4. Casting subclass objects
      5m 3s
    5. Understanding interfaces and implementing classes
      4m 2s
    6. Creating your own interfaces
      4m 14s
    7. Using abstract classes and methods
      6m 35s
  12. 32m 17s
    1. Managing files with the core class library
      7m 46s
    2. Managing files with Apache Commons FileUtils
      7m 32s
    3. Reading a text file from a networked resource
      7m 52s
    4. Parsing an XML file with DOM
      9m 7s
  13. 17m 39s
    1. Creating your own JAR files
      4m 54s
    2. Understanding the classpath
      5m 2s
    3. Documenting code with Javadoc
      7m 43s
  14. 47s
    1. Goodbye
      47s

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Java Essential Training
7h 17m Beginner Dec 14, 2011

Viewers: in countries Watching now:

Join author David Gassner as he explores Java SE (Standard Edition), the language used to build mobile apps for Android devices, enterprise server applications, and more. This course demonstrates how to install both Java and the Eclipse IDE and dives into the particulars of programming. The course also explains the fundamentals of Java, from creating simple variables, assigning values, and declaring methods to working with strings, arrays, and subclasses; reading and writing to text files; and implementing object oriented programming concepts.

Topics include:
  • Understanding the history and principles of Java
  • Installing Eclipse and Java
  • Compiling and running from the command line
  • Managing memory and performing garbage collection
  • Declaring and initializing variables
  • Writing conditional code
  • Building and parsing strings
  • Debugging and exception handling
  • Using simple arrays
  • Creating custom classes
  • Working with encapsulation, inheritance, and polymorphism
  • Managing files
  • Documenting code with Javadocs
Subjects:
Developer Programming Languages
Software:
Android Java Eclipse
Author:
David Gassner

Understanding the principles of Java

The Java programming language has been developed over the years following some very strict principles. The five principles of Java as declared when Java was created include, first, that it's a simple, object- oriented, and familiar language. Its simplicity lies greatly in its consistency. Once you learn how to do one thing in Java, you know how to do it the same way throughout the language because it never deviates from the way the language is architected. It's an object-oriented language. So once you understand the principles of encapsulation, inheritance, and polymorphism and how those are implemented in the Java programming language, you'll have a much better sense of how to architect your applications. And for developers who've worked with C-Style languages like C and C++, the syntax of Java is very familiar. Java was created to be robust and secure. Its robustness lies greatly in its object-oriented characteristics, because you're designing everything as an object, everything has methods or functions and properties also known as fields. And you create applications by combining multiple classes together. This lets you create your code in small chunks and it makes it easy to debug and maintain your applications over time. Java was designed to be portable, so that you'd be able to compile it once and then run your application on multiple operating systems and processors. Java was created to be high-performance. The original version of the Java Virtual Machine wasn't as fast as C++ applications, but over the years it's been improved enormously, and today Java applications run just as fast or sometimes even faster than applications built in C++. And finally Java was created as an interpreted language, it supports multithreading and it's dynamic. Interpreted, means that the application is compiled to a format that's interpreted at runtime rather than being run as machine code directly, this is what makes the applications portable. It's multithreaded, and it makes it easy to build applications that do more than one thing at the same time. And it's dynamic, in that it can change data types at runtime as long as those data types are compatible with each other. Here is the runtime architecture of Java. Again, it's an interpreted language, the application is compiled to bytecode rather than machine language, and that's what makes it portable between operating systems. Here is the software stat that's used at runtime when you run your application. You start with the operating system. You can run Java applications on Windows, Mac, Linux, Solaris, and any other operating system for which there is a usable Java Virtual Machine. The Java Virtual Machine you use most of the time will be the one provided by Oracle, the one that was created by Sun Microsystems, but there are other JVMs out there provided by IBM, the Virtual Machine that's provided for Android by Google and many others. On top of the Virtual Machine you add the core runtime and additional libraries. The core runtime is sometimes called the Java Class Library, and it consists of all of the functionality that's provided with the core Java developer toolkit. And finally your application runs on top of all that once again as compiled bytecode. So let's compare Java to a couple of popular languages. First C++, Java was originally created by C++ developers and they had in mind improving the developers' lot. Here are some ways in which Java is different from C++. If you're a C developer all of your code can be run in C++ as well. The two languages are compatible with each other, that's not true for Java. Even though Java has syntax that's very similar to C and C++, its code is unique. It has its own rules and its own syntax. I have mentioned earlier that C++ is compiled to native machine language and while that makes it very fast and gives it access to low-level functions, it means that your application has to be recompiled for each operating system and processor that you want to target. Java is compiled to bytecode. Because C++ is compiled to native machine language, it allows direct calls to the native system. In Java there is an interface called Java Native Interface sometimes called JNI, that lets you call those native functions through the JVM. C++ lets you write once and then as long as you followed standard C++ syntax you can recompile for each operating system you are targeting, whereas the principles of Java say that you can write once and run anywhere. Java runs in a protected virtual machine environment, and again, you have to go through that JNI interface to make those low-level system function calls. Here's a way in which the two languages are very different. C++ requires explicit memory management and uses pointers. C++ applications as a result can have memory leaks and it's up to the developer to make sure that they've sealed up all the holes in their application. In Java, memory is managed for you. When you create instances of classes or objects, the Java Virtual Machine automatically allocates the memory. And when you're done with the objects the JVM sweeps up the memory by destroying dereferenced objects, this is called the Garbage Collector. This means that in Java applications you don't have to know specifically how much memory is being used at any given time, you still have to pay attention to making sure that you only create the objects you need. And in C++ you can use multiple inheritance, this means that when you define an object you can inherit functionality for multiple super classes. The Java inheritance model is single inheritance so you can only inherit directly from a single superclass. This makes it easier to figure out where there are problems when your application has bugs. Let's also compare Java to JavaScript. Even though the names of these languages share the term Java, they are really not closely related. Java again wasn't compatible with previous languages even though it borrowed syntax from C. Java has morphed into a standard known as ECMA script or ECMAScript. Other languages that are based on the ECMAScript standard include Adobe's ActionScript 3.0 and JScript from Microsoft and a number of others. Java is compiled to bytecode and interpreted at runtime. JavaScript is interpreted directly from source code. Java can make native function calls through the JNI interface, while in JavaScript at least as it's implemented in a browser, is restricted to something called a browser Sandbox. It can only play in the Sandbox, and it can't make native function calls. Java is write once, run anywhere. JavaScript is even more portable in the sense that it has brought compatibility in many browsers and many operating systems. Java runs in a protected virtual machine but you have to explicitly have that virtual machine installed. And in a similar fashion JavaScript is executed by the browser and restricted to that browser sandbox for security. Both languages manage the memory for you, neither requires that you specifically allocate or deallocate memory. And in terms of inheritance, Java uses a traditional class-based inheritance where you define classes and then inherit their functionality. JavaScript uses something called prototype-based inheritance. This model allows you to add functions, properties, and other functionality to a pre-defined class at runtime, something Java doesn't allow you to do. So that's a look at the principles of Java and how you might compare this language to C++ and JavaScript. In the continuum of languages you might play C++ at the strictest level, Java somewhere in the middle, and JavaScript at the most dynamic. And you typically use Java when you want to build applications that rely on that language.

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